Primary signet-ring stromal tumour of the testis: case report with literature review.

Primary signet-ring stromal tumour of the testis (PSRSTT) is a very rare type of primary testicular tumour, which is not actually mentioned in the current WHO categorization of tumours of the male genital organs. In this case we report about histologically and immunohistochemically features of this rare tumour. In the present case, PSRTT was found in the orchiectomy preparation of a 69-year-old man with painless swelling of his left testicle. The tumour was well circumscribed and separated from the normal testicular tissue by a fibrous capsule. The tumour cells showed a signet-ring pattern and were separated by thin collagen bundles. No mitotic activity and necrosis were found inside the tumour. Immunohistochemically, the tumour was positive for vimentin, neuron-specific enolase (NSE), S-100 protein, β-catenin and cyclin D1. No expression of cytokeratin, actin, SALL4, OCT3/4, and especially, inhibin and calretinin were detected. In conclusion, the presence of signet-ring cell formation can be found in different tumours of the testis. PSRSTT is a rare tumour that needs to be considered, in particular, to distinct them from other tumours with signet-ring cell pattern.