Eosinophilic solid and cystic RCC - a case report of a rare entity.

Abstract

A 57-year-old female with an incidental finding of a 4 cm left renal mass on CT abdomen. Clinically, the patient was asymptomatic. The patient subsequently underwent a left radical nephrectomy. Microscopically, the lesion is composed of solid to nested cells with voluminous granular eosinophilic cytoplasm with characteristic basophilic intracytoplasmic inclusions. The features were consistent with an eosinophilic solid and cystic renal cell carcinoma (ESC-RCC). ESC-RCC is a novel and uncommon type of renal cell carcinoma, introduced as a distinct entity in the WHO 2022 kidney classification, and with only a few cases reported in the literature. The tumour displays characteristic CK20 and PAX8 positivity. Histological and immunohistochemical features are sufficient for diagnosis. This tumour is found more commonly in women with a broad age range of presentations. Of note, sporadic ESC-RCC consistently harbors TSC1 or TSC2 mutations and are similar but distinct from tuberous sclerosis complex associated renal cell carcinomas. Increased awareness of this entity with its characteristic architecture and immunophenotype can aid pathologists in making a definitive diagnosis.Copyright © 2024