Eosinophilic solid and cystic renal cell carcinoma with TSC2 mutation: a case report and literature review

BACKGROUND: Eosinophilic solid and cystic renal cell carcinoma (ESC-RCC) is an under-recognized, emerging new entity of sporadic renal neoplasms, which is listed as a rare type of renal cell carcinoma in the 2022 WHO renal tumor classification. It is easily misdiagnosed because its characteristics are insufficiently understood. CASE PRESENTATION: We report one case of ESC-RCC, a 53-year-old female patient with a right kidney mass found during clinical examination. The patient experienced no discomforting symptoms. Computer-tomography imaging at our urinary department showed a round soft tissue density shadow around the right kidney. Microscopic examination revealed a tumor displaying a solid-cystic composition of eosinophilic cells with unique features, revealed by characteristic immunohistochemical markers (CK20-positive/CK7-negative), and a nonsense mutation in TSC2. Ten months after the renal tumor resection, the patient presented in good condition with no recurrence or metastasis. CONCLUSIONS: The distinct morphological, immunophenotypic, and molecular characteristics of ESC-RCC we describe here, based on our case and the relevant literature, highlight the key points of the pathological and differential diagnosis of this novel renal neoplasm. Our findings will therefore deepen our understanding of this novel renal neoplasm and help reduce misdiagnosis.