Cytodiagnosis of benign fibrous histiocytoma of rib and diagnostic dilemma: a case report.

Benign fibrous histiocytoma (BFH) of bone is rare in occurrence, and rib is an unusual site. There are limited case reports of this entity in the literature, and cytodiagnosis of this tumor is not described. A 24-year-old man presented with a firm mass and pain in the right lateral chest wall. Radiological investigations (plain radiograph and computed tomography) revealed a lytic bone lesion involving the 5th rib. Radiologically, giant cell tumor (GCT), BFH, and plasmacytoma were suspected. In fine-needle aspiration cytology (FNAC), admixture of benign stromal cells and scattered osteoclast type giant cells were found in the smears. Differential diagnoses of BFH, GCT (non-epiphyseal type), fibrous dysplasia, and aneurysmal bone cyst were made on cytology. Subsequent histologic examination confirmed the diagnosis of BFH. Cytologic diagnosis of BFH of rib is difficult as this tumor may mimic other giant cell containing tumors of bone in FNAC. The final diagnosis should always be made after correlation with histological, radiological, and clinical features.