Surgical Pathology and Histopathology: Specimen to Diagnosis
Surgical Pathology and Histopathology tests specimen handling, gross description, frozen section, margin assessment, grading, staging, histologic typing and artifact recognition. The candidate must show that diagnosis depends on both morphology and context.
Core rules
- Fixation in neutral buffered formalin preserves morphology; inadequate fixation, cautery and crush artifact distort nuclei.
- Gross description includes site, size, shape, color, consistency, margins, distance to margins and lymph nodes.
- Frozen section answers a focused intraoperative question: malignancy, margin status or nodal metastasis. It is less accurate than permanent sections.
- Grading describes differentiation; staging describes anatomic extent and is usually the stronger prognostic factor.
- Margins must be oriented and sampled; a close margin is not the same as a positive margin.
- Immunohistochemistry resolves lineage and primary site but must be interpreted with morphology and controls.
Worked example
A 60-year-old undergoes right hemicolectomy for a 3-cm ascending colon tumor. The tumor penetrates muscularis propria into pericolic fat; 2 of 16 nodes are positive; margins are clear. The pathologic stage is pT3 pN1b. Reasoning: T3 means extension through muscularis propria into subserosa or non-peritonealized pericolic tissue; N1b means 2 to 3 positive nodes. Margin status and lymphovascular invasion are reported separately because they affect recurrence risk.
Traps
Do not use frozen section to distinguish subtle dysplasia from reactive change when permanent sections are needed. Do not call a margin positive because tumor is close. Avoid overcalling crush artifact as malignancy. Staging is not grading. A negative node biopsy does not exclude nodal disease if sampling is inadequate.