excisional biopsy
Summary
An excisional biopsy is the complete surgical removal of an entire lesion (often with a small rim of normal tissue) for histopathologic diagnosis. It is the preferred approach for suspected melanoma and for small, well-circumscribed lesions, because it preserves architecture and allows assessment of margins and depth (Breslow thickness).
Detail
**Definition:** Surgical removal of the entire lesion (mass, nodule, lymph node, or pigmented lesion), usually with a narrow margin of normal tissue, which is sent for histopathology. It is both diagnostic and potentially therapeutic.
**Biopsy types (high-yield comparison):** - **Excisional:** removes the whole lesion. Best for suspected melanoma (narrow 1–3 mm margins), small masses, and lymph nodes (removes the entire node for lymphoma architecture). - **Incisional:** removes only part of a large lesion. Used for large masses, such as suspected soft-tissue sarcoma, where excision could compromise later definitive surgery. - **Core needle:** a cylinder of tissue that preserves architecture. Used for breast masses and many other solid tumors. - **Fine-needle aspiration (FNA):** cells only (cytology), with no architecture. Used for thyroid nodules and cystic lesions. It cannot distinguish follicular adenoma from carcinoma, because that requires capsular and vascular invasion on histology. - **Punch:** a 2–8 mm full-thickness skin sample. Used for inflammatory dermatoses and some small lesions. - **Shave:** superficial. Used for suspected basal or squamous cell carcinoma, and it is not appropriate for suspected melanoma because it can transect the lesion and prevent Breslow depth measurement.
**Clinical significance:** - **Melanoma:** excisional biopsy with 1–3 mm margins is preferred. Breslow thickness (measured in mm from the granular layer to the deepest tumor cell) is the most important prognostic factor. Do not use wide margins at biopsy, because that can disrupt later sentinel lymph node mapping. Definitive wide local excision follows based on thickness (about 1 cm for ≤1 mm, 1–2 cm for 1–2 mm, 2 cm for >2 mm). - **Lymphadenopathy:** excisional node biopsy is preferred over FNA for suspected lymphoma (Reed-Sternberg cells in Hodgkin lymphoma, architecture in non-Hodgkin lymphoma). - **Breast:** excisional biopsy (often after needle localization) is used for lesions that are discordant or atypical on core biopsy (e.g., atypical ductal hyperplasia, radial scar, papillary lesions). - **Sarcoma:** incisional or core biopsy is preferred, with the biopsy tract placed along the planned resection line.
**Advantages:** Provides the whole specimen for diagnosis, shows architecture and invasion, lets pathologists assess margins, and can be curative for benign or early lesions.
**Disadvantages and risks:** More invasive than needle techniques. Risks include bleeding, infection, scarring, and wound dehiscence. It may require anesthesia, and an inappropriate incision can complicate later definitive surgery.
**Test-taking pearls:** - Suspected melanoma → excisional biopsy with narrow margins (not shave, and not wide excision up front). - Suspected lymphoma → excisional lymph node biopsy. - Thyroid nodule → FNA first. - Large suspected sarcoma → incisional or core biopsy, with careful planning of the incision. - Orient the specimen and mark margins for the pathologist.
Sources
- First Aid for the USMLE Step 1
- Robbins & Cotran Pathologic Basis of Disease
- Schwartz's Principles of Surgery
- Sabiston Textbook of Surgery
- NCCN Guidelines: Melanoma, Cutaneous
- AAD Guidelines of Care for the Management of Primary Cutaneous Melanoma
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