Fine-needle aspiration of granulocytic sarcomas: a morphologic and immunophenotypic study of seven cases.

Granulocytic sarcoma is an uncommon extramedullary, solid tumor of myeloid cells. Only rarely has this entity been diagnosed by fine-needle aspiration (FNA) cytology. This report encompasses the cytologic findings of FNAs from seven patients with granulocytic sarcomas, including four male and three female patients with a mean age of 52 years (range, 12 to 77 years). The aspirates were obtained from skin or subcutaneous tissue (four cases), testis (one case), posterior ileum (one case), lymph node (one case), and abdominal washing (one case). Morphology of the aspirates varied from well-differentiated to poorly differentiated cells showing little or no evidence of myeloid differentiation. Thorough search for evidence of myeloid differentiation and a high index of suspicion of granulocytic sarcoma are of paramount importance. In three cases, flow cytometric and immunocytochemical studies were applied to the FNA materials to confirm the myeloid lineage of the cells and the diagnosis. In the other four cases more than one site was involved by the tumor; once the diagnosis of granulocytic sarcoma was established with a biopsy, the FNA sufficed to confirm the diagnosis at another location. This study demonstrates that FNA cytology in conjunction with appropriate immunophenotyping can provide an accurate diagnosis of granulocytic sarcoma. Fine-needle aspiration can reduce the need for surgical intervention when combined with immunophenotypic studies and when additional anatomic sites are involved.