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Pathology · single question

A biopsy shows fibrous stroma with multinucleated giant cells and hemosiderin (brown pigment). Lab shows elevated PTH and hypercalcemia. What is the diagnosis?

  1. Central giant cell granuloma (CGCG)
  2. Brown tumor of hyperparathyroidism
  3. Ameloblastoma
  4. Aneurysmal bone cyst
Show answer and explanation

Correct answer: B. Brown tumor of hyperparathyroidism

Brown tumors occur in hyperparathyroidism (primary or secondary). They are histologically IDENTICAL to CGCG — fibrous stroma, multinucleated giant cells, hemosiderin. The distinction is biochemical: elevated PTH + hypercalcemia = hyperparathyroidism → brown tumor. Without elevated PTH, the same histology = CGCG.
  • A. ❌ CGCG is histologically identical but lacks elevated PTH/hypercalcemia — biochemistry distinguishes them.
  • B. ✅ Brown tumor of hyperparathyroidism — elevated PTH + hypercalcemia + CGCG-like histology = pathognomonic combination.
  • C. ❌ Ameloblastoma shows follicular/plexiform epithelial patterns — completely different histology.
  • D. ❌ Aneurysmal bone cyst has blood-filled spaces with fibrous walls — different histologic appearance.

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