Primary Leydig cell tumour of epididymis: a rare case report with review of literature.

Leydig cell tumour (LCT) is an uncommon tumour that typically occurs in the testis. Primary epididymal LCT is extremely rare. To the best of our knowledge, only two cases have been reported in the world literature. Herein, we report a case of primary epididymal LCT in a 41-year-old Chinese male. The patient presented with right epididymal swelling for 3 months without endocrine manifestations, including gynaecomastia and decreased libido. Scrotal ultrasound demonstrated a mass about 1.5 cm in diameter entirely in the cephalic region of right epididymis. No abnormality was found in his bilateral testes. The patient underwent total mass resection without post-operative therapy. Histological examination revealed that the well-circumscribed tumour was separated by conspicuous hyalinised fibrous stroma; the tumour cells were large and polygonal with round nuclei and abundant eosinophilic cytoplasm. Immunophenotypically, the tumour cells expressed four markers of sex cord differentiation (calretinin, melanA, CD99 and inhibin). There was no recurrence at 2-year follow-up. Our observation once again confirms that LCT could primarily occur in the epididymis, and we suppose that it probably originates from the ectopic Leydig cells. As little is known about the pathogenesis and prognosis for such a rare disease, accumulation of more pathological and clinical data can help to better interpret this tumour.