Synchronous Leydig Cell Tumor and Seminoma in the Ipsilateral Testis


Leydig cell tumor is a rare sex cord tumor that accounts for 1–3% of all testicular neoplasms. Seminomas are more common and occur in 30–40% of testicular tumors. Leydig cell tumors are derived from undifferentiated gonadal mesenchyme and the concurrent development of the tumor and a seminoma which are derived from germinal epithelium in an ipsilateral testis is extremely rare.

Case Report

A 38-year-old male with no significant medical history presented at our institution with 5 months' history of increased left testicular swelling. Physical and ultrasound examination was suspicious for a testicular mass. Computed tomography scan of the abdomen was unremarkable and showed no lymphadenopathy. Preoperative hormone levels and tumor markers were unremarkable.


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.


The immunohistochemical results supported the concurrent diagnosis of Leydig cell tumor and seminoma in a unilateral testis. The patient was followed up with imaging studies with no evidence of disease progression. The patient is currently stable, 10 years after surgery. 


Leydig cell tumors are rare testicular tumors that occur predominantly in the adult population. In children and adolescents, Leydig cell tumors are associated with precocious puberty and macrogenitosomia.The adult patient is usually asymptomatic and typically presents with testicular enlargement. However, some patients may present with gynecomastia or decreased libido, which is usually related to the overproduction of estrogens. Majority of Leydig cell tumors are benign, but 10% of cases are malignant.No single pathologic criterion clearly defines a malignant Leydig cell tumor, but factors favoring a malignant behavior include large tumors (>5 cm), infiltrative borders, a high mitotic rate (>3 per high power field), cytologic atypia, vascular invasion, tumor necrosis, and extratesticular extension.However, a tumor with predominantly benign features on gross or microscopic examination can metastasize and this occurs usually late in the course of the disease. Seminomas are more common testicular tumors of germ cell origin. They either occur de novo or in association with other germ cell tumors such as yolk sac tumors or embryonal carcinoma.The coexistence of Leydig cell tumor, a gonadal stromal tumor, and seminoma, a germ cell tumor, in an ipsilateral testis is extremely rare. To date, only 5 cases, including our patient, have been reported in the literature. A review of all the cases showed that the mean age of the patients was 33.8 ± 5.9 years.Only one case was associated with cryptorchidism and decreased libido due to elevated estrogen levels. The size of the Leydig cell tumors ranged from 1 to 1.5 cm, and their small sizes correlate with the benign nature of all 5 cases.All 5 cases were associated with seminoma; only one case had additional findings of embryonal carcinoma and choriocarcinoma. Three cases were treated with radical orchiectomy and 2 cases were treated with radical orchiectomy and adjuvant radiotherapy. For the 2 cases that reported outcomes, survival was 10 and 16 years, respectively. 


Synchronous Leydig Cell Tumor, Seminoma, Ipsilateral Testis

Author : Ifeyinwa E. Obiorah et al