Fine needle aspiration cytologic diagnosis of focal intrahepatic extramedullary hematopoiesis.

A computed tomographic scan in an 80-year-old man with a urinary obstruction demonstrated a solitary space-occupying liver lesion, which was clinically suspected to be a metastatic carcinoma. Fine needle aspiration (FNA) of the mass produced a smear containing atypical, possibly malignant, cells. Correlation of the FNA findings with the patient's history resulted in a cytologic diagnosis of an intrahepatic focus of extramedullary hematopoiesis (EMH). This case shows FNA biopsy to be a reliable method of diagnosing foci of EMH, but also demonstrates the potential pitfall of diagnosing atypical megakaryocytes as malignant in FNA smears. EMH should be considered in the differential diagnosis of patients with bone marrow disorders and mass lesions in extramedullary sites.