PA 530 Derm Diagnostics

how does an excisional biopsy work?

-a scalpel removes the entire lesion, plus a few mm around the lesion -requires sutures to close -all tissue sent to lab where pathologist makes a diagnosis: may cut in half and send 1/2 to histology and 1/2 for cultures -correlate path with clinical data to make the final diagnosis and treatment plan

how does magnification work?

-apply drop of mineral oil, then visualize -hand lens or binocular (7x) or microscope (5-40x)

what is a benefit and risk of intradermal allergy testing?

-benefit: more sensitive -risk: highest rate of false positive, highest risk for anaphylaxis

what are indications for shave biopsy?

-benign-appearing lesions or elevated -nodular lesions suggestive of BCC or SCC -seborrheic keratoses or AKs, skin tags, warts, and superficial BCC or SCC

what are benefits of dermoscopy?

-can measure changes -can send to experts for review -utilized frequently in telemedicine

what is oblique lighting?

-darkened room, light from the side -allows better evaluation of slight elevations and depressions/area affected, contours, shadows, or any abnormalities

how does percutaneous allergy testing work?

-drop of solution with allergen placed on skin -needle pierced through the drop - + reaction causes wheal to form within 20 minutes -watch for anaphylaxis

what are benefits of punch biopsy?

-easily mastered -low infection rate

what are examples of findings that can be examined through magnification?

-follicular plugging -- systemic lupus erythematous (SLE) -Wickham striae -- lichen planus -BCC -- translucence and telangiectasia -melanoma -- subtle changes in color (blue and grey)

how does acetowhitening work?

-gauze saturated 5% acetic acid swabbed over area -5-10 minutes later inspection of area with 10x magnification hand lens -warts will be white papules

what can microscopic examination incorporate?

-gram stains -cultures

what are indications for punch biopsy?

-inflammatory lesions such as psoriasis, eczema, or drug eruptions -when you think it might be a malignancy

how does intradermal allergy testing work?

-inject allergen under patient's skin, forming a wheal

what are indications for excisional biopsy?

-lesions requiring complete removal or pigmented lesions/melanoma -any lesion not adequately covered by punch biopsy -when tissue needs to be studied for culture, histopathology, microscopy, or immunofluorescence (multiple things) -large lesions

how does dermoscopy work?

-magnification 10x to 30x using a hand lens + light -some are digital cameras and image lesions

what is subdued lighting?

-natural, gentle lighting -enhances contrast between lesions and normal skin -allows appreciation of subtle changes

what are contraindications for excisional biopsy?

-no absolute contraindications, but should only be selected when other options are not ideal

what are contraindications for punch biopsy?

-not effective if lesion is large (size and depth) -some locations

what are contraindications for shave biopsy?

-pigmented lesions -NOT appropriate for melanoma -can't assess depth -shave biopsy sites typically heal more slowly than excisional biopsies -can leave a scar

how does microscopic examination for suspected scabies work?

-place oil on scalpel -place oil on burrow or papule -scrape suspected papules/burrows and remove top of papule -transfer oil to slide and view under microscope -look for mites, ova, or feces

what are examples of lesions that do not blanch due to vasculitis?

-purpura (purple-colored spots/patches) -ecchymosis (discolored skin due to bleeding underneath) -petechiae (tiny spots of bleeding under the skin)

how does patch allergy testing work?

-small amount of substance placed on skin in shallow cups or "Finn chambers," taped, left for 24-48 hrs -contact hypersensitivity causes papular vesicular reaction within 48-72 hrs

how does a punch biopsy work?

-sterile round scalpel (1-8 mm diameter) -removes a circle of the lesion and has a depth that reaches the underlying superficial fat -results in a core of tissue -using index and thumb rotate punch cutting through epidermis, dermis, and subcutaneous tissue -send for histology

how does a shave/tangential biopsy work?

-sterile surgical blade is held horizontal to the skin and shaves off a more superficial sample of the lesion -no sutures needed -leaves scar, slightly depressed, same size as lesion

what are examples of lesions that can be identified through acetowhitening?

-subclinical penile/vulvar warts -cervical lesions (pre-cancerous)

when is a skin biopsy indicated?

-to diagnose: if a lesion is of unknown etiology -when you need confirmation: to determine treatment options or for insurance reasons -when the patient needs confirmation: therapeutic biopsy

how does KOH prep work?

-use dull scalpel to scrape areas of dry skin for skin cell samples onto slide -drop KOH over slide, place coverslip on top -gently heat for ~1 minute -gently flatten/separate cells -look for hyphae present in fungus

how does a woods lamp work?

-utilizes long wave ultraviolet light or "black light" -365 nm -make fluorescent pigments visible

how does microscopic examination for herpes work?

Tzanck prep/smear -gentle curettage with scalpel -smear on slide -Giemsa, Wright stain, or methylene blue -look for multinucleated cell

what does diascopy evaluate?

blanching of lesion

what color does a woods lamp turn erythrasma?

coral red (interdigitum infection from Corynebacterium)

what is magnification used for?

examination in greater detail of lesions for classic findings

what color does a woods lamp turn dermatophytosis?

green to yellow (tinea capitis or fungal infection of the scalp hair)

what is dermoscopy used for?

inspection of pigmented lesions

how does diascopy work?

press glass slide against skin

how does a skin biopsy work?

small excision taken under local anesthesia that may cause bleeding and leave a small scar -obtain written consent -may require sutures -samples going for histopathology should be placed in formalin -send tissue with brief but detailed clinical information -results usually arrive from the lab 5-10 days later

when is microscopic examination indicated?

suspected bacteria or yeast, scabies, herpes, or fungal infection

what is an important aspect of dermatologic diagnostics?

visual inspection/amplification and perception