Lesson 4: Necropsy & Veterinary Oncology

Client education to discuss during chemotherapy

Chemotherapy involves a substantial amount of necessary client education. Clients should be instructed to do the following: Avoid direct contact with urine, feces, or vomitus. Walk pets in a sunny, low-traffic area away from children. Use gloves when changing litterboxes or cleaning up the pet's accidents in the home. Monitor for potential side effects, and give medications as directed to reduce these side effects (such as antiemetics).

Administration of chemotherapy

Chemotherapy must be administered carefully to decrease the risks to the patient of serious side effects. Aggressive or unruly patients may need sedation to allow adequate restraint. Doses should always be checked multiple times to avoid a potentially fatal overdose. Injectable chemotherapy drugs often must be administered via intravenous catheter. Many chemotherapy drugs are vesicants, meaning that they'll cause severe skin irritation and sloughing if they escape the pet's vein.

Palliative Treatment

Palliative care is intended to improve the pet's quality of life without curing the disease. Palliative care may be used in the case of incurable cancers or when client finances don't permit aggressive treatment. Palliative care focuses on relieving pain, lethargy, inappetence, nausea, diarrhea, and other signs that may be associated with cancer. In most cases, these goals are accomplished through medications (pain medications, antiemetics, and appetite stimulants). In some cases, palliative care is provided using surgery, radiation, or chemotherapy. Even if this treatment isn't expected to cure the cancer, decreasing tumor size may improve patient comfort.

Gross pathology

Pathological changes that are visible with the naked eye

Histopathology

Pathological changes that require a microscope to observe

How to perform a large animal necropsy in pigs

Pig necropsy is similar to small-animal necropsy. Gastrointestinal disease is a common cause of death in pigs, so special attention should be given to examining the intestines and collecting multiple samples as early in the necropsy as possible. The nasal turbinates should also be examined, which requires cutting the snout.

How to perform a large animal necropsy in ruminants

The preliminary steps of a ruminant necropsy are relatively similar to the procedure in small animals, beginning with the animal in left lateral recumbency. Once the abdomen is open you may need to nick the rumen to reduce gas distension. The intestines are opened while still attached to the mesentery. The thoracic organs are typically also accessed via the abdominal incision due to the difficulty associated with cutting the ribs. Samples from the brainstem, pharyngeal lymph nodes, and tonsils may be required to test for prion diseases.

Discuss the process of staging cancer.

The process of staging cancer considers the following four aspects of an oncologic disease. The histologic appearance of the tumor and its grade can help determine which staging tests need to be performed. 1. The location and type of the tumor 2. Tumor size and its borders 3. The involvement of regional lymph nodes 4. The presence or absence of metastasis and the number of tumors

Pathogenesis

The sequence of events that leads to or underlies a disease

Oncology

The study of cancer

Cytology & Histology of cancer

To diagnose cancer, cancerous cells must be viewed under a microscope by a pathologist. This requires a biopsy—a sample of fixed tissue that the pathologist can examine. Biopsies may be incisional (removing a small sample of a larger mass) or excisional (removing an entire mass and sending all or part of it to the pathologist). In some cases, cytology may be used for a preliminary diagnosis. This test involves using a needle to aspirate a small number of cells from the mass, then spraying these cells onto a slide for staining and microscopic examination. Cytology is often performed for skin tumors and occasionally for other types of masses.

Chemotherapy

Use of chemical substances to treat a disease; usually refers to use of cytotoxic drugs to treat cancer

When does cancer occur?

When abnormal cells fail to die

How to dissect the neck & thoracic viscera in small animals during necropsy

When you're ready to move on to the chest, you'll take the "pluck" that you freed up earlier and remove it from the chest, along with the heart and lungs. Each component must be cut open individually and examined thoroughly, including the heart. Specific cuts are recommended when dissecting the heart to allow the visualization of all chambers and structures.

High-grade vs low-grade tumors

High-grade tumors are expected to behave aggressively, while low-grade tumors are typically less aggressive in behavior.

Types of cancer treatment

1) Surgery Surgery can't be used on all masses, but it can be used in the case of solitary masses that haven't metastasized. In some cases, surgery can be curative. Surgery may also be used in conjunction with chemotherapy (in the cases of tumors likely to metastasize) or radiation (in the cases of tumors that tend to be locally invasive) to provide a better chance of resolution. 2) Radiation Radiation is used to kill cancer cells and shrink tumors. In some cases, this is done with curative intent, in which case the radiation is often combined with other treatments such as surgery. In other cases, radiation is given for palliative care, intended to decrease pain and improve the patient's quality of life. Radiation doesn't affect tumor cells only; it also has effects on healthy surrounding tissue. Some patients develop skin reactions, known as acute radiation toxicity, during treatment. 3) Chemotherapy Technically, chemotherapy refers to the use of any medications or drugs to treat cancer. In general use, chemotherapy refers to the use of a small group of drugs that stop cell proliferation and kill tumor cells by altering DNA. Chemotherapy can be given orally or by injection. Often, chemotherapy involves periodic large doses of drugs with recovery time between doses. Some chemotherapy plans involve small doses of medications given daily. Chemotherapy drugs typically target active, rapidly dividing cells. This means that chemotherapy tends to have effects on not only cancer cells but also gastrointestinal cells, neutrophils, platelets, and cells within the hair follicles. For this reason, side effects may include vomiting, diarrhea, inappetence, and hair loss (in some breeds).

Outline all of the steps for an entire necropsy procedure of small animals.

1. Before you begin dissection, make sure you have the owner's permission, the correct animal's body, disposition instructions, body weight, labeled formalin container, instruments, cassette for bone marrow, tag for the brain, cardboard for nerve and skin, and an understanding of the clinical history. 2. All routine tissues and all lesions are collected, all lesions are described (measured and weighed, if appropriate), and all necessary microbiological, cytologic, and toxicologic samples and formalin fixed tissues are collected for every necropsy. 3. Weigh the animal, and perform the external examination; remove the eyes, then place the body in left lateral recumbency; make a midline skin incision extending into axillary and inguinal areas to reflect limbs; extend the incision rostrally to the mandibular symphysis and caudally to the perineum. 4. Dissect and examine, section, and collect (DESC) skin, lymph nodes, salivary glands, and testes or mammary glands. Open coxofemoral, stifle, and scapulohumeral joints. DESC the synovium, skeletal muscle, sciatic nerve, and bone marrow. 5. Open the abdomen (midline), puncture the diaphragm, open the chest (bilateral, cutting ribs) and the pericardium, collect microbiological samples, and examine organs and vessels in situ. DESC the thyroid, parathyroids, and adrenal glands. 6. Remove tongue from the oral cavity, and reflect the tongue, tonsils, larynx, and esophagus caudally. Cut the spinal cord and vertebral column at the atlantooccipital joint, remove skin and muscle from the calvaria, cut the calvaria with Stryker saw in hood, and remove the caudal-dorsal calvaria and the dorsal meninges. Transect the cranial nerves, and remove the brain and the pituitary gland. Open the tympanic bullae. Section the head longitudinally, and examine nasal and oral cavities. 7. Remove the tongue, tonsils, esophagus, trachea, lungs, heart, and thoracic aorta together. Serially section the tongue, open esophagus, and trachea. Open the right atrium, followed by the right ventricle, and then follow the pulmonary arteries, isolate the heart, and open the left atrium, left ventricle, and thoracic aorta. Weigh the heart. Collect the whole heart in cats and small dogs and three sections of the heart in larger animals. Serial section the lungs, saving one section from each lobe. 8. Remove the distal duodenum, jejunum, ileum, colon, and mesenteric lymph nodes together by stripping from the mesentery (open later unless critical). Remove the liver, duodenum, pancreas, stomach, and spleen en bloc. Serially section the spleen, open the stomach and duodenum, express the gallbladder, weigh the liver, and serially section the liver (collect one section of each lobe). Open the gallbladder, stomach (collect fundus and pylorus), duodenum, and pancreas (one section of right lobe with duodenum and one section of left lobe). Collect samples from all tissues. 9. Remove the floor of the pelvis, and DESC the right kidney and ureter, left kidney and ureter, urinary bladder, urethra, prostate, ovaries and uterus, cervix and vagina, rectum, anal glands, and abdominal aorta then DESC the small intestine, colon, and mesenteric lymph nodes. 10. Remove the spinal cord, if necessary.

8 fundamental characteristics of cancer cells

1. Cancer cells stimulate their own growth. 2. Cancer cells are insensitive to inhibitory signals that would stop their growth. 3. Cancer cells evade programmed cell death. 4. Cancer cells can multiply indefinitely. 5. Cancer cells stimulate the growth of blood vessels to supply their own nutrition. 6. Cancer cells invade local tissues and can spread distantly. 7. Cancer cells have abnormal metabolic pathways. 8. Cancer cells evade the body's immune defenses.

Basic steps involved in necropsy include:

1. Weigh the patient. 2. Perform an external exam of the patient, assessing for wounds, parasites, or other visible abnormalities. 3. Collect samples for histopathology, cytology, bacteriology, virology, parasitology, and toxicology (depending on clinical history), including formalin-fixed and fresh samples. 4. Describe all gross findings in the necropsy report. Include digital photos, if possible.

Decontamination & Waste Disposal of Chemotherapy

A spill kit must be easily accessible in case of spills, and it's important to know how to use the kit. Any contaminated PPE should be removed immediately and disposed of in a sealed bag inside a hazardous waste container. Contaminated skin should be scrubbed thoroughly with soap and water. Medical attention may be required if a rash develops on affected skin and doesn't show signs of improvement within one hour. Eye contamination should be addressed by using an eyewash for a full 15 minutes.

Process of removing the skull & brain during small animal necropsy

After examining the mouth, you'll cut the muscles of the jaw to allow the tongue, larynx, pharynx, trachea, and esophagus to be reflected back over the chest as a single unit. This tissue is sometimes referred to as "the pluck." Once the pluck has been removed, an incision is made in the ventral atlanto-occipital joint. This allows the skull to be removed after the skin has been peeled back. Once the skull has been removed, a saw can be used to create three cuts in the skull. These cuts allow removal of the intact brain.

How to dissect the urogenital tract during necropsy of a small animal

After removing the abdominal organs, you'll be able to access the pelvic floor to assess the reproductive organs. The kidneys can be pulled away from the body wall with their ureters intact; the ureters should be cut near the bladder. The bladder should be opened for examination as well as the urethra and prostate (if a male). The abdominal aorta, rectum, and anal sacs can also be removed and examined at this time.

Teratogen

Agent or substance that may cause physical defects in a developing embryo if a pregnant female is exposed to the substance

Vesicant

Agent that causes tissue destruction or necrosis on extravasation

How to view the abdominal cavity during necropsy of a small animal

All of the abdominal organs must be removed from the abdominal cavity for thorough evaluation. When doing so, be sure to clamp or tie off the duodenum and colon to prevent intestinal contents from contaminating the rest of the abdomen. After all of the other organs have been removed and examined, the intestines can be cut open for thorough evaluation.

Malignant tumor

An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body via blood & lymphatic vessels; a cancerous tumor.

Malignant & Benign tumors

Both malignant and benign tumors may grow large locally and cause discomfort. Unlike benign tumor cells, malignant cells are invasive and destroy surrounding tissue.

What tissue samples should be collected for histopathology?

Brain Lung Heart Liver Spleen Pancreas Stomach Small intestine Colon Kidneys Lymph nodes Bladder Muscle

How should lesions be noted during a necropsy?

By using the following characteristics: Location Number Color Size Shape Distribution Consistency Odor

Adjuvant Therapy

Cancer treatment that's given in addition to the primary or initial treatment

Types of cancers based upon tissue of origin?

Carcinomas arise from epithelial tissues (skin, mucous membranes). Sarcomas arise from mesenchymal tissues (bone, cartilage). These 2 broad tumor types are further classified according to the tumor's specific tissue of origin - ex: a sarcoma that arises from bone is an osteosarcoma

Mutagen

Chemical or physical agent that causes permanent DNA injury and alteration within a cell

Adverse Event Classifications

Grade 1: Mild or asymptomatic effects only. Intervention is not indicated. Grade 2: Moderate to mild effects. Outpatient intervention is needed. Grade 3: Medically significant but non-life-threatening. Hospitalization is needed. Grade 4: Life-threatening. Urgent intervention and intensive care is needed. Grade 5: Death.

Side Effects & Adverse Reactions

Chemotherapy side effects vary based upon particular treatments. In general, most side effects are mild. A small number of patients may develop more serious side effects that require hospitalization. This is more likely in patients that already have some sort of underlying disease as well as in herding breeds with the multidrug resistance gene. The following three significant side effects may occur with chemotherapy: Anaphylaxis: Although rare, life-threatening allergic reactions to chemotherapy can occur. Many patients receive diphenhydramine before chemotherapy to reduce the likelihood of anaphylaxis. Acute tumor lysis syndrome (ALTS): This condition is most common in pets with leukemia or lymphoma. Signs often occur within hours to days of their first treatment and are related to rapid tumor cell die-off. Affected pets often show depression, vomiting, diarrhea, and rapid deterioration. This condition is usually fatal. Neutropenia: Neutrophils are more affected by chemotherapy than other white blood cells due to their short lifespan and rapid turnover. Neutrophil levels often reach their lowest five to seven days after chemotherapy; neutrophil counts below 1,000/µL indicate a significantly increased risk of infection.

Imaging of cancer includes

Chest radiographs are often a first step toward identifying the presence of metastatic disease. Additionally, radiographs may be performed on any masses or other abnormalities noted on an exam. In some cases, more specialized testing such as an ultrasound, CT scan, or MRI may be recommended.

Complementary, Alternative, & Integrative Medicine

Complementary, alternative, and integrative medical therapies may be used in many areas of veterinary medicine, including oncology. - Alternative medicine uses alternative therapies in place of standard medical therapies. - Complementary medicine uses nonstandard treatments to complement standard medical therapies. - Integrative medicine incorporates conventional, complementary, and holistic therapies in a rational, evidence-based way. Many veterinarians and oncologists incorporate some degree of integrative medicine into their practices. Yunnan Baiyao is an herbal supplement that's widely used by veterinarians to stop bleeding, and acupuncture may help with pain control and improve patient quality of life.

Discuss how imaging can be used to evaluate a patient.

Comprehensive radiography of the thorax is most commonly used initially to evaluate the presence or absence of metastatic disease. Specialty hospitals may additionally recommend thoracic computed tomography (CT), depending on the type of tumor and its location. It is the imaging modality used for planning radiation therapy, as it is more likely to 730detect very small lesions compared with other imaging modalities. Before performing expensive, invasive, or risky treatments, it is important to properly stage a patient's cancer, particularly if metastasis is likely. Patients undergoing CT must be either anesthetized or sedated, which can increase risk to an unhealthy patient. In addition, CT is not widely available and can be more expensive than radiography. Therefore, CT is not recommended for every case, and initial survey radiography is recommended to detect obvious lesions. For abdominal imaging, ultrasonography is currently the diagnostic method of choice in veterinary medicine. Abdominal ultrasonography is noninvasive and allows better visualization of organs compared with radiography. Ultrasonography can also guide percutaneous collection of biopsy samples and body cavity effusions.

Myelosuppression

Condition in which normal bone marrow activity is decreased, resulting in fewer white blood cells, red blood cells, and platelets in the circulation

Cosmetic necropsy vs Full necropsy

Cosmetic necropsy: the patient's internal organs are removed for examination without disrupting the external appearance Full necropsy: more thorough but doesn't leave cosmetic remains available for the owner

Primary goal of necropsy + additional goals

Determine the cause of death, but also allow for discovering signs of other diseases that may have occured during the animal's life Also allows confirmation of the accuracy of P's clinical diagnosis + evaluation of the positive & negative effects of any treatments that were performed on the patient

How to ship necropsy specimens

Diagnostic sample packaging must be labeled with a designated symbol. Containers must be leak-proof and shouldn't be susceptible to breakage. Primary containers should be placed inside of a secondary container (such as a sealed plastic bag) to collect any leakage. This should then be placed into a rigid shipping box with plenty of cushioning. Fresh tissue samples should be shipped with freezer packs. Refrigeration isn't needed for formalin-fixed samples. Submission forms should be placed in a separate plastic bag to protect them from moisture.

Necropsy

Examination of an animal after it has died to determine abnormal and disease-related changes that occurred during its life

Safe Handling Practices of chemotherapy

Exposure to chemotherapy drugs is a concern from both a personal safety and an environmental contamination standpoint. There's no known safe level of exposure, and many chemotherapy agents are teratogens, mutagens, and carcinogens, so actions must be taken to limit exposure as much as possible. When handling chemotherapy drugs, personal protective equipment (PPE) must always be worn. This should include a gown, gloves (ideally thick, chemotherapy-rated gloves), mask, and eye protection (such as goggles). Chemotherapy drugs should also be handled in a ventilated biological safety cabinet, with syringes of medication drawn up using a closed system safety device (CSTD) to reduce aerosolization. Chemotherapy drugs should always be handled and prepared in a dedicated room with low traffic flow. The room should have ventilation that can be turned on during treatments. No eating or makeup application should occur in a chemotherapy room.

Describe fetal necropsy

Fetal necropsy is challenging because samples are often autolyzed and mummified due to time spent in utero after death. Still, fetal tissues and fetal membranes can provide valuable information in cases of abortion. A fetus is typically necropsied in right lateral recumbency to allow easier access to organs. Samples are often taken for both viral culture (lung, liver, kidney, spleen) and bacterial culture (stomach fluid, lungs, liver).

Common tumors in horses include:

Fibromas are benign tumors that typically affect the frog of the hoof. Surgical removal is curative. Melanoma/melanocytoma tumors are common on hairless regions of middle-aged to older gray horses. They may be benign or malignant. Squamous cell carcinomas are thought to be caused by sun damage and often occur on hairless skin (genitals, eyelids). These tumors are locally invasive and may require aggressive surgical removal. Sarcoids are the most common skin tumor in horses. The exact cause of sarcoids is unknown, but viral infection is suspected.

Describe the difference between cytology and histology and list the advantages and limitations of each.

Histologic examination of the primary tumor is performed by an anatomic pathologist to confirm the diagnosis of cancer. The procedure requires a sample of tumor tissue obtained through either incisional or excisional biopsy. Excisional biopsy attempts to remove the entire tumor and a margin of normal tissue, whereas incisional biopsy procures only part of a tumor. Incisional biopsy may be used before definitive treatment for larger tumors located in complicated locations. Neoplastic tissues and/or associated lymph nodes are collected and preserved in a fixative, such as formalin. Samples are submitted to a pathology laboratory for processing and interpretation by an anatomic pathologist. FNA is another helpful sampling technique. It may be performed concurrently with a biopsy, or it may be performed independently. Cytology samples obtained from FNA are stained with modified Wright-Giemsa stain and are submitted to a laboratory service for interpretation by a clinical pathologist. Technicians should be careful not to expose cytology slides to formalin, as partial fixation of cells can alter cell morphology. Some slides can be stained in-house with Diff-Quik or a similar stain and then evaluated immediately by the clinician. Cytology does not usually require anesthesia or sedation and allows for more rapid assessment and identification of cancer cells, if present in the sample. However, biopsy is often still needed to confirm the diagnosis and the tumor grade. Cytologic diagnoses correlate strongly with biopsy diagnoses, but not necessarily vice versa. Some tumor types, such as sarcomas, are poorly exfoliative, which means the absence of cancer cells in a cytology sample does not always rule out cancer. Cytology is recommended at the start of a workup for most cutaneous lesions. It rarely requires sedation and is often performed using a 22-gauge needle, 6- to 10-mL syringe, and multiple slides. The needle is inserted into the lesion of interest, and a sample is obtained either by "coring" the sample using a poking motion under the skin or by using light suction with a 10-mL syringe attached to the needle. Cells in the needle hub are sprayed onto slides by using the syringe, and another slide is then used to carefully spread the cells on the first slide. Slides are then stained for microscopic evaluation.

How to perform a large animal necropsy in horses

Horses are also necropsied in left lateral recumbency. Overall, the procedure is similar to necropsy in ruminants, though the method of removing the intestines from the abdominal cavity is slightly different. Additionally, horses have guttural pouches, which must be examined closely for signs of disease.

Describe avian necropsy

If a bird is suspected of having an infectious or zoonotic disease, the bird should be submitted whole to a diagnostic laboratory. If necropsies are done in-house, it's important to wear a mask and to first soak the carcass in disinfectant or warm, soapy water to reduce the threat of zoonotic disease and the irritation that feathers and dander may cause. Birds are placed in dorsal recumbency and opened along the ventral midline. Small birds can be pinned to a corkboard by the wings to help stabilize the body. The chest and abdomen are both opened, similar to the technique used in small animals. Depending on the size of the bird, tissue samples may need to be removed for fixation. Or, it may be possible to place the whole bird in fixative once the body cavities have been opened.

Cosmetic necropsy

In a cosmetic necropsy, only the chest and abdomen are opened. An abdominal incision is made from the sternum to the pubis, allowing the abdominal organs to be examined and removed. The thoracic organs are examined and removed by removing the diaphragm. After removing the organs, the body cavity is filled with paper towels (to absorb fluids) and the abdominal incision is sutured closed.

What side effects do tumors lead to?

In addition to the pain, inflammation, and other local effects of tumors, some tumors also result in paraneoplastic syndromes. These tumors release molecules that can lead to systemic effects, such as hypercalcemia (most common), hypoglycemia, disseminated intravascular coagulation, anemia, hyperproteinemia, fever, muscle wasting, and others.

Discuss how to perform rabies procedure.

In all cases where rabies is suspected, the animals should be handled only by clinicians and technicians who are preimmunized against rabies and have a serum titer greater than 1 : 5. For small animals, prosectors should double-glove and wear protective masks and goggles. For animals larger than large dogs, personnel should wear rubber boots, a scrub suit, an apron, double gloves (the outer glove is heavy vinyl with gauntlets), and a face shield for splash protection. Pathology personnel who decapitate and extract brains must use the additional protection of a Tyvek coverall or alternatively a surgical gown and apron. A high-efficiency particulate air (HEPA)-filtered helmet and face shield are suggested when working on equine species because of concerns about aerosolization of West Nile virus. In suspected cases of rabies the head should be carefully removed by disarticulation at the atlantooccipital junction using a disposable scalpel or knife, double-bagged, placed in a refrigerated container (with ice packs, not dry ice), and sent to the appropriate laboratory for fluorescent antibody testing. The remaining carcass should be double-bagged in a red biohazard bag, labeled as a rabies suspect, and disposed of as a biological hazard. Some states require removal of the brain before submission to the laboratory for animals larger than a large dog (horses, cattle, etc.). To remove the brain of a large animal for rabies testing, use a special head vise or hold the head on the table (eyes may be removed to facilitate head holding). Remove as much hide and flesh over the calvaria as possible. The rostral transverse cut through the skull is made behind an imaginary line connecting the lateral canthi of the eyes. Lateral saw cuts start at the dorsolateral notch of the occiput and just miss the dorsal projection of the coronoid process. A small hatchet, inserted into the saw cuts, can be used to lever the calvaria. Then, cranial nerves and meningeal attachments can be severed and the brain removed. Hemisection, parasagittal section, or selective subsection of the brain should be performed for the rabies laboratory submission, as directed by the state testing laboratory. In cases where a human has been bitten or exposed to saliva through open wounds, and rabies is not on the differential list or the animal did not have neurologic signs, either the whole head or two transverse slices of the brain (one involving the medulla and cerebellum bilaterally and the other involving the hippocampus bilaterally) should be submitted for rabies testing. The necropsy can be performed in the usual manner. In all cases, tables and instruments must be carefully disinfected and cleaned. Disposable scalpels are placed in a sharps container, and other instruments must be cleaned and disinfected. All submitted tissues must be accompanied by a completed state rabies questionnaire.

In Situ

In its normal place or location of origin

Describe what is involved in an initial data base for a patient.

Initial evaluation of oncology patients includes a CBC, accompanied by blood smear examination, a serum chemistry profile, and urinalysis. Other common staging diagnostics include three-view thoracic radiography, abdominal ultrasonography, lymph node palpation, and cytology.

When should necropsy be performed? Why?

It should be performed as soon after death as possible to avoid autolysis (decomposition)

Common tumor types:

Lymphoma is a cancer of the immune system that tends to cause dramatic, widespread lymph node enlargement in dogs. Cats also develop lymphoma, but they instead tend to develop gastrointestinal signs because the lymphoma infiltrates the intestines. Mast cell tumor is the most common malignant skin tumor in dogs. Mast cell tumors can also occur in cats. With early treatment, most mast cell tumors carry a relatively good prognosis. Mast cell tumors contain granules that are full of histamine and other chemical mediators. These chemicals can be released with manipulation, leading to systemic effects. Osteosarcoma is a bone tumor that often occurs in large-breed, middle-aged dogs. Affected dogs develop lameness due to pain associated with the tumor. Oral tumors have different causes. Dogs most commonly develop melanoma, while oral tumors in cats are most likely to be squamous cell carcinoma. Signs include difficulty eating and loosening teeth, with no evidence of dental disease. Hemangiosarcoma is a cancer that often arises in the spleen or liver of middle-aged to older, large-breed dogs. Dogs typically present for a history of acute collapse, which occurs due to abdominal bleeding.

Describe laboratory animal necropsy

Most lab animal patients can be necropsied using the traditional small-animal necropsy technique. Given the focus on herd health in lab animal medicine, much more extensive testing may be required in a lab animal necropsy.

When may mutations be present?

Mutations may be present at birth (germ line mutations) or may occur over time during somatic cell division. The latter type may be attributed to carcinogens or mutagens (such as UV radiation)

Describe the facilities, instruments, and supplies needed to perform a necropsy, including protective clothing.

Necropsies should be performed in a well-lit, well-ventilated space that's easy to clean and disinfect. Protective clothing should be worn, including gloves, a mask, scrubs, or other easily changed clothing. Mesh gloves are available to prevent cuts, especially when working with large animal patients (which typically involves the use of large knives). Equipment used for necropsies should be kept separate from equipment used in treating patients to prevent contamination.

Fresh tissues + considerations

Often collected for microbiological (bacteria, virus, fungus) and infectious disease testing & toxicology Typically placed in sterile containers w/o preservatives or in a Culturette Collect with sterile instruments & store in refrigerator (do not freeze unless sample is used for toxicology) Should be collected from primary disease site

Process of small animal necropsy involving superficial organs, skin, & limbs

Place the animal in left lateral recumbency. Make an incision from the right axilla to the mandibular symphysis, then extend this incision caudally to the perineum. Dissect between the scapula and ribs to allow the upper forelimbs to be reflected, then dissect the coxofemoral joint to reflect the hind limbs. Next, rotate the animal into dorsal recumbency, and incise down the medial aspect of the limbs. As you remove the skin, you'll be able to examine the lymph nodes, mammary glands, skin, and testes. You should also open the joints to examine the joint space and joint fluid. Collect samples as needed, then proceed to open the three major body cavities (peritoneal, pleural, and pericardial). The abdomen can be opened via a midline incision from the sternum to the pubic symphysis. Once the abdomen is open, puncture the diaphragm to check for negative pressure before opening the chest, then cut through the ribs with pruning shears or scissors. After opening the chest, you can open the pericardium and examine the heart.

Explain the principles of preliminary and external examination of the carcass.

Preliminary Observations Before the necropsy is begun, the prosector should review the signalment (species, breed, color, sex, age, weight, and animal identification), the clinical history, and available laboratory data. External Examination The exterior of the animal is examined for any abnormality or lesion, and external parasites, such as ticks and lice. The body conformation, hair coat, skin, nose, mouth (lips, cheeks, gums, teeth, and tongue), eyes (eyelids, conjunctiva, cornea, sclera, anterior chamber, iris, and lens), ears, mammae, penis, prepuce, scrotum, vulva, anus, and feet should be examined. Because the retina decomposes rapidly after death, dissection begins with the eyes. The upper and lower eyelids are examined and excised. The membrana nictitans is grasped with tissue forceps, the globe is lifted, and soft tissue attachments to the bony orbit are incised with scissors or a scalpel in a 360-degree arc. As the globe is freed from the orbit, care must be taken to avoid application of excessive tension to the optic nerve. The optic nerve is carefully severed at the optic canal. The excised globe is examined. Then extraocular muscles, fascia, fat, conjunctiva, and membrana nictitans are dissected from the globe. The interior of the eye can be examined by immersing the globe in clear, cool water. The sclera is examined, and the unopened globe is immersed in Bouin solution or formalin

Preliminary testing of cancer

Preliminary testing includes a complete blood cell count, serum chemistry profile, and urinalysis. These tests provide an assessment of the patient's overall health and may provide information related to the tumor, in some cases.

Fixed tissues + considerations

Samples that are preserved to prevent further decomposition after collection. Often used for histopathology. Sample should go directly from patient to the fixative; & NOT rinsed with water or rubbed with fingers When multiple samples are placed into a single container, clip-on tags are used to identify similar samples (for example, "right kidney" versus "left kidney"). Tissue cassettes can also be used, which allow small samples to be contained separately within a larger container. Samples should be small to allow adequate penetration with formalin. In general, samples should be no more than 1 cm thick. When placing samples into a container, there should be 10 times as much formalin in the container as there is tissue. If larger samples must be fixed intact, 50 percent formalin is often used instead of the typical 10 percent formalin; this allows better tissue penetration. Formalin must be handled with care because it's a contact irritant and a carcinogen. Use gloves and eye protection, and store formalin carefully.

Autolysis

Self-digestion of tissues or cells by enzymes released by their own lysosomes

Clinical signs of cancer:

Signs are highly variable, but common signs include: Nonhealing skin swellings or wounds Weight loss Marked decrease in appetite Exercise intolerance Difficulty urinating, breathing, or defecating Persistent discharge from nasal passages or other orifices

Cancer that is common in cattle

Squamous cell carcinomas Associated with sun exposure & typically occur in open-range cattle with limited access to shade

Staging vs Grading of tumors

Staging describes how large a tumor is and how far it has spread in the body. Staging requires additional testing, such as ultrasound, CT scans, bloodwork, and lymph node biopsies. Grading describes how aggressive the tumor is expected to be, based on cellular characteristics observed by the pathologist.

Pathology

Study of disease

Swabs & fluids + considerations

Swabs may be collected for bacterial culture, virus isolation, and other testing. These samples should be collected and shipped in a sterile manner. Use a Culturette, if available, to keep the slide from drying out. If you don't have access to a Culturette, swabs can be placed in a plain, red-top tube with a few drops of sterile saline for moisture. Fluid samples collected prior to euthanasia or immediately after can also prove valuable when interpreting necropsy results. These samples can be submitted to the lab if available.

Paraneoplastic Syndrome

Symptoms that result from effects on organs or tissues distant from the site of a primary tumor or its metastases, usually caused by a substance that's released into circulation

How to dissect the vertebral column & spinal cord during necropsy of a small animal

The method of spinal cord removal varies depending on the patient's size and clinical history. In general, samples of the vertebrae and spinal cord should be removed for evaluation and sampling.

Process of small animal external examination & dissection (what should be dissected first?)

The necropsy starts with a thorough external evaluation of the animal. Record the patient's signalment and any relevant information gained through external evaluation. Next, you'll begin your dissection. There are two principles of dissection that are typically followed in necropsy: Each part of the body is first examined in situ, then removed from the body for closer evaluation as a whole, then dissected and examined. As each organ is removed, it's processed to completion (all samples collected) before moving on to the next organ. The eyes should always be dissected first because the retina decomposes more quickly than other organs. Each globe should be removed from the orbit, examined, and placed in formalin.

Explain how to write a necropsy report

While necropsy is performed, all abnormalities should be described & recorded. After necropsy is completed, a report should be written, including tentative conclusions (diagnoses) at the end of the report. Includes signalment, too. All lesions are described and recorded by using the following criteria (examples are given in parentheses): • Location (caudal, cranial, dorsal, ventral, left, right) • Number (one, two, hundreds) • Color (red, green, yellow-tan) • Size (e.g., 3 × 5 × 4 cm, or weights for liver and heart) • Shape (round, flat, spherical, stellate) • Distribution (focal, multifocal, diffuse) • Consistency (soft, firm, hard, rubbery) • Odor (sweet, sour, ammonia) Findings are usually recorded in the order in which they were encountered in the necropsy. The descriptions should be as specific as possible without drawing conclusions.

Benign tumor

a mass of abnormal cells that remains at the site of origin; doesn't spread to distant sites

Metastasize

the process by which cancer spreads from one place to another

List and discuss the indications for a necropsy.

• To determine the cause of death, which can be due to infections (bacteria, viruses), parasites, toxins, trauma, neoplasia, nutritional deficiencies, metabolic diseases, and congenital or hereditary diseases • To determine the disease process or processes that led to the animal's death • To determine the accuracy of the clinical diagnosis • To evaluate the positive and negative effects of therapeutic measures In situations in which more than one animal is at risk, as in multiple-animal households, farms, and laboratory animal facilities, a necropsy is helpful in determining whether other animals are at risk for infection, inherited conditions, or injury caused by toxins or environmental hazards. In addition, necropsy gives the technicians the opportunity to increase their knowledge about anatomy of various animal species each time one is performed.