A pheochromocytoma that is malignant is defined by which criterion?
- A Presence of metastases in non-chromaffin tissue (lymph nodes, liver, bone, lung) ✓
- B Mitotic figures >5 per 50 HPF
- C Tumor size >5 cm
- D Capsular invasion on histology
Correct answer: A. Presence of metastases in non-chromaffin tissue (lymph nodes, liver, bone, lung)
Explanation
Malignancy in pheochromocytoma cannot be determined by histological features alone (unlike most tumors); it is defined solely by the presence of metastases to sites where chromaffin tissue is not normally found, such as lymph nodes, liver, bone, and lung. Histological features like capsular invasion, increased mitoses, or necrosis raise suspicion but are not definitive. The PASS (Pheochromocytoma of the Adrenal gland Scaled Score) and GAPP scores help risk-stratify but do not diagnose malignancy.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.