Fine‐needle aspiration of brown tumor of bone: Cytologic features with radiologic and histologic correlation

We report the case of a 40‐year‐old man with tertiary hyperparathyroidism due to end stage renal disease who initially presented with acute‐onset paraplegia, elevated serum parathyroid hormone, and multiple bone abnormalities, including a large extradural intraspinal mass seen by magnetic resonance imaging. In contrast with imaging features, fine‐needle aspiration cytology showed numerous benign‐appearing multinucleated osteoclast‐type giant cells that are the characteristics of either brown tumor or benign giant cell tumor of bone. Sheets of mononuclear spindled stromal cells were also noted. A core‐needle biopsy confirmed the diagnostic features of brown tumor of hyperparathyroidism. Diagn. Cytopathol. 2009. © 2008 Wiley‐Liss, Inc.