Surgical Pathology: From Gross to Diagnosis
Surgical pathology questions probe the workflow: specimen handling, margin assessment, frozen section triage, and the language of synoptic reporting. The candidate must understand what the surgeon needs and what the pathologist can and cannot answer intraoperatively.
Concepts to master
- Specimen orientation and inking: margins are assessed by ink; a "close" margin is defined by distance, and the definition varies by organ (e.g., breast vs. prostate vs. skin).
- Frozen section indications: determine margin status, confirm malignancy vs. benign, assess lymph node metastasis, and identify tissue (e.g., parathyroid). It is unreliable for lesions requiring permanent-section architecture (e.g., some thyroid follicular lesions) and for fatty or calcified tissue.
- Margin terminology: negative, close, and positive; "R0/R1/R2" in oncologic resection maps to microscopic and macroscopic residual disease.
- Synoptic reporting: pTNM staging requires size, invasion depth, node counts, and margin status; the pathologist's report is the staging document.
- Frozen artifact: cautery artifact, crush artifact, and freezing artifact can mimic atypia - a classic trap.
Traps
The most common error is choosing frozen section for a diagnosis it cannot reliably make. Another is confusing "margin positive" (tumor at ink) with "close" (tumor near ink). Also watch for questions that conflate lymph node count with nodal positivity - the number of nodes examined matters for staging adequacy even when all are negative.
Rule of thumb
Ask: Does the intraoperative decision change based on the answer? If yes, and the tissue is amenable, frozen section is appropriate. If the diagnosis requires permanent architecture or immunohistochemistry, defer.
Worked example
A lumpectomy for invasive ductal carcinoma shows tumor 1 mm from the inked margin. This is a close margin, not positive (tumor not at ink), and in breast conservation the modern standard generally accepts "no tumor on ink" as adequate for invasive disease - so re-excision is not automatically required. The trap answer is "positive margin, re-excise."