Micropapillary Serous Borderline Tumor With Microinvasive Low-Grade Serous Carcinoma of the Tunica Vaginalis Harboring NRAS p.Q61R Mutation: Expanding the Molecular Spectrum of Paratesticular Müllerian-Type Tumors.

Serous tumors of the testis and paratestis are rare neoplasms originating from Müllerian duct epithelium, exhibiting histological features analogous to their ovarian counterparts, predominantly manifesting as serous borderline tumors and low-grade serous carcinomas. Definitive diagnosis of these tumors requires histopathological examination and immunohistochemical profiles to confirm Müllerian differentiation. This study reports the first documented NRAS p.Q61R mutation as a likely pathogenic variant (Class II) and a BRCA2 variant of uncertain significance (Class III) in a tunica vaginalis micropapillary serous borderline tumor with microinvasive low-grade serous carcinoma. While NRAS mutations are infrequently observed in ovarian serous tumors, their presence in this context suggested potential shared oncogenic pathways between male and female Müllerian-type neoplasms. Notably, the NRAS p.Q61R variant was classified as Class II and may be associated with malignant progression from borderline tumors to invasive carcinoma. These findings underscore the need for long-term surveillance and molecular investigations to clarify tumor behavior, recurrence risks, and therapeutic targets in such rare entities.