Malignant leydig cell tumor

Histology: The testis was almost entirely replaced by a tumor consisting of solid sheets of cells with abundant eosinophilic cytoplasm. There was a spectrum of atypia ranging from relatively uniform cells with round uniform nuclei to larger more pleomorphic cells, some multinucleated. Nucleoli were prominent, although mitotic figures were infrequent. Focal necrosis was present along with focal spindling of the tumor cells. Occasional tumor cells had abundant xanthomatous cytoplasm.
Discussion: This tumor does not resemble any of the germ cell tumors. It is not as pleomorphic as embryonal carcinoma which also has some attempt a luminal formation, lacking in the current case. Areas of the tumor with more bland cytology are typical of a Leydig cell tumor. Criteria for malignancy in Leydig cell tumors are: pleomorphism; frequent mitoses (>3/10HPF); atypical mitoses; vascular space invasion; infiltrative edges; necrosis; and size >5 cm. In the current case, the presence of marked cytological atypia, necrosis, and large size would qualify for a malignant leydig cell tumor. Sarcomatoid differentiation in a leydig cell tumor is extremely rare with only a few case report. In the current case, the sarcomatoid features are not fully developed, but some of the tumor cells show a spindle cell morphology which is further diagnostic of a malignant leydig cell tumor.
Sarcomatoid Leydig cell tumor: Histopathology 1995; 27: 578-80