Microcystic stromal tumour of testis.

Within the group of gonadal sex cord-stromal tumours, microcystic stromal tumour (MCST) is a rare entity. In the literature, most case series and reviews discussed MCST arising in the ovary, only one case-report concerned a testicular MCST. We present a Caucasian man in his late 30s, who presented with an MCST in his right testis. The tumour was encapsulated and composed of vaguely lobulated cellular nodules and cystic spaces with bland spindle cells and hyalinised fibrous stroma. By immunohistochemistry, the tumour cells expressed cluster designation 10, androgen receptor, steroidogenic factor-1 and nuclear beta-catenine, and there was focal nuclear expression of cyclin D1. Molecular diagnostics confirmed the presence of an exon 3 mutation (c.98C>T) in the CTNNB1 gene. These features are similar to MSCT described in the ovary. Clinical follow-up (more than 1 year) was uneventful.Although the clinical and radiological presentation was that of a possible malignant testicular lesion, this entity is benign.