BACKGROUND: Osteoclastic giant cell carcinoma (OGC) is an uncommon variant of ductal carcinoma of the pancreas. It is important to differentiate this variant from other giant cell pancreatic lesions, particularly the more aggressive pleomorphic giant cell carcinoma. CASE: Aspiration cytology was performed in a case of OGC. Aspirates of OGC demonstrated three populations of discohesive cells: (1) large, bizarre, pleomorphic malignant giant cells with high nuclear/cytoplasmic ratios, irregular nuclear membranes and coarse chromatin; (2) spindle or small mononucleate cells; and (3) bland, osteoclastlike epithelial giant cells with multiple small, round, central nuclei and prominent nucleoli. CONCLUSION: Multinucleate giant cells can be seen in pancreatic abscesses, fat necrosis, pseudocysts, tuberculosis, sarcoidosis and fungal infections. When the cells are associated with malignant epithelial cells, the differential diagnosis includes metastatic carcinoma, malignant melanoma, Hodgkin's disease, large cell anaplastic lymphoma, trophoblastic tumor, epithelioid sarcoma, malignant fibrous histiocytoma, angiosarcoma and rhabdomyosarcoma. Immunohistochemical stains, such as vimentin, S-100, leukocyte common antigen, human chorionic gonadotropin, Factor VII Ag, actin and desmin play an important role in differentiating between these lesions.
