Testicular Leydig cell tumor diagnosed on fine needle aspiration.

We report on the cytopathologic findings of a Leydig cell tumor of the testis in an adult male with no evidence of endocrine dysfunction. The preoperative diagnosis was based on fine needle aspiration cytology (FNAC) and was subsequently confirmed on histomorphology. The cytologic smears were cellular and showed tumor cells arranged singly, as well as in dyscohesive clusters. The tumor cells were large, round to polygonal, with indistinct cytoplasmic margins and pale, abundant, granular to vacuolated cytoplasm. A few intranuclear Reinke's crystals that are considered pathognomonic and essential for the diagnosis were seen. The present case was of interest because of the scarcity of literature on the cytodiagnosis of this tumor. The use of FNAC for diagnosis may vitiate the need for more invasive biopsy procedures in the preoperative diagnosis of this rare testicular tumor. Copyright 2009 Wiley-Liss, Inc.