Sertoli cell tumor of the testis (not otherwise specified) with the expression of neuroendocrine markers and without the expression of inhibin-alpha.

Sertoli cell tumor of the testis (not otherwise specified) in a 43-year-old man is reported. Macroscopically, the testicular mass measured 3.0 x 2.3 x 1.5 cm and was well circumscribed. The cut surface was white to tan-gray in color. Neoplastic cells with eosinophilic cytoplasm proliferated with solid and tubular structures. Neoplastic cells focally contained vacuoles of various sizes in the cytoplasm. Cystic formation and cord formation in the hyalinized stroma was also observed. Immunohistochemically, neoplastic cells were positive for cytokeratin 8, chromogranin A and synaptophysin, but neoplastic cells were negative for placental alkaline phosphatase, inhibin-alpha and pancytokeratin. The stroma in the tumor center and capsule contained a significant number of myofibroblasts that were positive for alpha-smooth muscle actin and negative for h-caldesmon, but no CD34-positive stromal cells were detected in the stroma of the tumor center. Ultrastructurally, neoplastic cells had cytoplasmic processes and abundant rough endoplasmic reticulum and lipid droplets in the cytoplasm. However, dense core granules were absent. It is important to differentiate between Sertoli cell tumor and carcinoid tumor because of the positive reaction for neuroendocrine markers in both tumors. Myofibroblasts are a major stromal component of Sertoli cell tumor of the testis.