A left radical inguinal orchiectomy was performed and the specimen was submitted for histopathological examination. Pathological examination revealed a well-circumscribed tan-pink fleshy mass with lobular appearance and focal hemorrhage measuring 6 cm and occupied 80% of the testis. A distinct second small tan-white nodule (1 cm) close to the tunica albuginea was also identified.
Both masses were found alongside each other with intervening fibrous septa. Histological sections of the first mass showed nests of tumor cells with clear cytoplasm with intervening fibrous bands and lymphocytes, which was consistent with a provisional diagnosis of seminoma.
Microscopic examination of the small nodule revealed polygonal cells with eccentric nuclei, eosinophilic, granular, and vacuolated cytoplasm, mild atypia, and rare mitosis, which was consistent with a tentative diagnosis of a Leydig cell tumor. Based on the rarity of the provisional diagnosis, it was important to rule out other neoplasms such as a clear cell sex cord-stromal tumor or a clear cell carcinoma.
On immunohistochemistry, neoplastic cells from the large mass were positive for CD117, placental alkaline phosphatase (PLAP), and CD10 and negative for inhibi, cytokeratin, β-catenin, smooth muscle actin (SMA), synaptophysin, desmin, S100, β-HCG, and α-fetoprotein. These results confirm the diagnosis of seminoma and exclude the diagnosis of a sex cord tumor or carcinoma. MIB-1 proliferative index was 80% in the seminoma cells.
The Leydig cell tumor showed strong positivity for inhibin and vimentin and was negative for CD117, PLAP, cytokeratin, β-catenin, SMA, synaptophysin, desmin, S100, CD10, β-HCG, and α-fetoprotein. Approximately 10% of the tumor cells stained positively for MIB-1. Based on the findings, a diagnosis of a benign Leydig cell tumor was made.