Surgical Pathology Flashcards

A 55-year-old man undergoes excision of a pigmented skin lesion. Histology shows atypical melanocytes extending into the reticular dermis with a Breslow thickness of 2.5 mm. What is the recommended excision margin according to UK guidelines?

Answer: 2 cm

UK (BAD/NICE) guidelines recommend excision margins based on Breslow thickness: 4 mm = 2-3 cm. A Breslow thickness of 2.5 mm therefore requires a 2 cm margin. Sentinel lymph node biopsy should also be discussed.

Which histological feature distinguishes Crohn's disease from ulcerative colitis?

Answer: Non-caseating granulomas

Non-caseating granulomas are the hallmark histological feature of Crohn's disease, found in approximately 60% of surgical specimens. While crypt abscesses and pseudopolyps can occur in both conditions, they are more characteristic of ulcerative colitis. Crohn's features transmural inflammation, skip lesions, and granulomas, while UC shows continuous mucosal/submucosal inflammation.

A 60-year-old woman has a breast lump biopsied. Histology shows cells arranged in single file (Indian file pattern) with signet ring morphology. Which type of breast cancer is this most consistent with?

Answer: Invasive lobular carcinoma

The Indian file pattern (single-cell linear infiltration) and signet ring cells are characteristic of invasive lobular carcinoma (ILC). This is due to loss of E-cadherin, a cell adhesion molecule, caused by CDH1 gene mutation. ILC accounts for 10-15% of breast cancers and may be bilateral. It can be difficult to detect on mammography due to its diffuse growth pattern.

A thyroid fine-needle aspirate is reported as Thy 3f (follicular neoplasm). What is the recommended management?

Answer: Diagnostic hemithyroidectomy

Thy 3f indicates a follicular neoplasm that cannot be distinguished from follicular carcinoma on cytology alone — the distinction requires assessment of capsular or vascular invasion on histology. The standard management is diagnostic hemithyroidectomy (lobectomy) to obtain a definitive histological diagnosis. If carcinoma is confirmed, completion thyroidectomy may be required.

Which molecular marker is most commonly associated with hereditary non-polyposis colorectal cancer (Lynch syndrome)?

Answer: Microsatellite instability (MSI) due to mismatch repair gene defects

Lynch syndrome is caused by germline mutations in DNA mismatch repair (MMR) genes — MLH1, MSH2, MSH6, or PMS2. This leads to microsatellite instability (MSI-H), causing accumulation of mutations in microsatellite repeat sequences. APC mutations are associated with familial adenomatous polyposis. Screening involves immunohistochemistry for MMR proteins and MSI testing.

A patient undergoes gastrectomy for gastric cancer. The pathology report describes a linitis plastica appearance. Which WHO histological subtype is most commonly associated with this macroscopic pattern?

Answer: Diffuse (poorly cohesive/signet ring cell) type

Linitis plastica (leather bottle stomach) is characterised by diffuse thickening and rigidity of the gastric wall. It is associated with the diffuse type (Lauren classification) or poorly cohesive/signet ring cell type (WHO classification). These tumours infiltrate submucosa and muscularis, inciting a desmoplastic stromal reaction. They carry a worse prognosis than intestinal-type tumours.