Adrenal cortical carcinoma (ACC) is distinguished from adrenal cortical adenoma using the Weiss scoring system. Which histological feature carries the highest discriminatory weight?
- A Tumour weight greater than 100 grams
- B Presence of lipid-poor cells comprising more than 25% of tumour
- C Mitotic rate greater than 5 per 50 high-power fields
- D Vascular invasion (into endothelium-lined spaces within or beyond the capsule) ✓
Explanation
The Weiss criteria include nine histological features scored 0 or 1; a total score of 3 or more indicates malignancy. The three most diagnostically reliable and weighted features are: high mitotic rate (>5/50HPF), atypical mitoses, and vascular or capsular invasion. Vascular invasion (tumour invading into endothelium-lined vascular channels within or beyond the capsule) is particularly pathognomonic of malignancy and is one of the most discriminatory single features. Lipid-poor (eosinophilic, clear-cell-scarce) cells comprise another Weiss criterion but are less specific. Tumour weight is a gross criterion, not a Weiss histological criterion.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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