Eosinophilic solid and cystic renal cell carcinoma: A rare under-recognized indolent entity.

Eosinophilic solid and cystic renal cell carcinoma (ESCRCC) is an under-recognized, emerging new entity of sporadic renal neoplasms, with an approximate incidence of 0.2% of renal tumors. A total of 60 cases have been reported in the literature till date. ESCRCC are usually seen in adult females, with a low stage and indolent behavior, and rare incidence of recurrence or metastasis. They are solid and cystic tumors with variably sized cysts resembling eosinophilic RCC, showing a characteristic positive immune-expression for PAX-8, CK20 (in ~80% cases) and/or Melan-A (in ~6.7%), with negative CK7 and CA-IX expression. They consistently harbor TSC1 or TSC2 mutations in all tumors, which is a proposed molecular marker for this entity. We here present the first reported case of this rare tumor from India. The tumor was positive for PAX-8, and showed diffuse strong positivity for Melan-A, while was negative for CK7 and CK20. It was an early-stage tumor (T1), managed with partial nephrectomy, with no evidence of any recurrence/metastasis after 1 year of follow-up.