Intranuclear Reinke's crystals in a testicular Leydig cell tumor diagnosed by aspiration cytology. A case report.

Fine needle aspiration cytologic findings in a Leydig cell tumor of the testis are described. Besides the rarity of case reports on fine needle aspiration cytologic diagnosis of this tumor, the present case was of interest because of the finding of numerous intranuclear and intracytoplasmic Reinke's crystals as well as some lying free between the cells. In a few cells the intranuclear crystals were seen to orient themselves in a row, with a nipplelike protrusion of the nuclear membrane as if being pushed by the crystals. Besides the well-formed crystals, many nuclei showed irregular, thin, groovelike spaces that may have been earlier stages of crystal formation. These findings suggested the intranuclear formation of Reinke's crystals. Extranuclear crystals were seen to fuse in pairs and hence to appear thicker than the intranuclear crystals. The crystals lying free between the cells also showed a linear arrangement in places. The crystals were more numerous with May-Grünwald-Giemsa (MGG) staining. Intranuclear crystals were seen only in MGG-stained smears.