Leydig cell tumor of the testis: a cytohistological, immunohistochemical, and ultrastructural case study.

We report a case of Leydig cell tumor of the testis in a young man, in whom preoperative diagnosis was achieved by fine-needle aspiration biopsy cytology. Cytology, histology, and ultrastructural examination showed diagnostic Reinke's crystals, both in nuclei and in cytoplasm. Immunohistochemistry displayed strong vimentin and estrogen positivity.