Dermatopathy (Skin Biopsy Guidelines):

Question 1

General Rules:

Answer 1

-Biopsy is an important diagnostic tool but may NOT provide definitive diagnosis
-IS a guide for treatments, additional tests, and is needed for consultation

Question 2

What should be biopsied:

Answer 2

-Diseases most readily diagnosed by biopsy
-Lesions not responding to presumptive appropriate treatment
-Lesions that are unusual or appear serious
-Nodular lesions, including suspected neoplasias
-Pustular and bullous lesion
-Alopecia disorders not due to grooming or pruritic
-Lesion that necessitates a definitive diagnosis before treatment

Question 3

General Site Selection Rules:

Answer 3

-Individual lesions are typically heterogeneous, some areas are diagnostic and some are not
-No surgical preparation of the skin recommended prior
-Essential to collect primary skin lesions as they are the most diagnostic

Question 4

Nodule Site Selection:

Answer 4

-Directly in the nodule/bump
-Elliptical wedge biopsies are best suited for solitary nodules that can be entirely excised as well as deep nodular lesions in the panniculus

Question 5

Erosion & Ulcer Site Selection:

Answer 5

-Clinical signs consistent with an autoimmune blistering skin disease:
-Mucosal or mucocutaneous ulcerations and erosions
-Bilaterally symmetrical distribution, especially on the face
-#1: Never biopsy an entirely ulcerated area
-#2: Select new lesion, which may be proximal to an ulcerated lesion
-#3: Prefer wedge biopsy across the margin of normal and ulcerated skin
-#4: Multiple biopsies from representative areas of various stages
-#5: Biopsy before instituting glucocorticoid therapy
-8mm or 6mm punch biopsy:
-Margin of lesional to non-lesional skin
-Take multiple biopies from representative areas of various stages
-Margin of large ulcerated lesions and 8mm punch biopsy of small early lesions

Question 6

Alopecia Site Selection:

Answer 6

-Primary Lesions: Cushing’s disease or vaccine-induced vasculitis
-Secondary lesions: Allergies
-If alopecia is the primary lesion, then collect multiple skin biopsies central to most alopecic area and marginal of healthy to healthy areas

Question 7

Sample Prep and Submission:

Answer 7

-General: 10% buffered formalin is standard but think first before dunking!
-With really small pieces: Cassette it
-Neoplasm: Ink margins and/or use sutures for orientation
-Fresh tissue for culture/PCR: Place each tissue in separate tubes with enough sterile saline to keep moist; If you use a whirl-pak bag, wrap tissue in sterile moistened gauze; Fresh tissue is usually better than swab
-Getting samples ready for submission: Put everything in separate containers unless in labeled cassette; Label everything appropriately; ALWAYS give history to pathologist; Discontinue oral corticosteroids and immunomodulatory therapies prior to biopsy

Question 8

After submitting the tissue:

Answer 8

-Submitted Tissues: Will be embedded in paraffin wax and stained with hematoxylin & eosin
-Histochemical stains (Special stains): Look at etiologic agents, specific cell types, type of pigment, fibrosis, amyloids, fibrin
-Immunohistochemistry: Etiologic agents, tumor types, prognostication
-Interpreting the report: Gross pathology, histopathology, diagnosis (Morphologic, etiologic, is it a disease or condition), comment (Read comment carefully!!)