Malignant Leydig-cell tumor of the testis diagnosed by fine-needle aspiration using ThinPrep technique.

Leydig cell tumors (LCT) are rare sex cord-stromal tumors that account for 2-3% of all testicular tumors. Approximately 10% of LCTs shows evidence of malignant behavior. We present a case of LCT with severe atypia diagnosed by fine-needle aspiration (FNA) in a 49-year-old man who presented with gynecomastia and right testis enlargement. The FNA material on conventional and ThinPrep smears revealed a hemorrhagic and necrotic background with high cellularity, consisting of large cells, isolated or in small cohesive clusters, abundant, eosinophilic cytoplasm, round nuclei, fine chromatin, and variably conspicuous nucleoli. Occasionally, pleomorphic cells with hyperchromatic nuclei and prominent nucleoli were seen. Immunocytochemistry was positive against vimentin, inhibin, and calretinin. Histological examination of the surgical specimen was in accordance with the FNA findings. The cytologic diagnosis of LCT of the testis, using FNA, is achievable in a preoperative setting to vitiate the need for more invasive biopsy procedures; malignancy could be considered on cytology when necrosis and marked atypia are evident.