Eosinophilic Solid and Cystic Renal Cell Carcinoma: From Unclassified to Classified, A Case Report.

Eosinophilic solid and cystic renal cell carcinoma (ESC RCC) is a novel tumour with unique morphological and immunohistochemical features. It is a recently described entity after the 2016 World Health Organization Classification of Tumours of the Urinary System and Male Genital Organs and is characterised by a solid cystic tumour composed of polygonal cells with voluminous eosinophilic cytoplasm and CK20 positivity. This tumour has uncertain malignant potential and also has an association with tuberous sclerosis complex (TSC). Sarcomatoid differentiation has not been reported in ESC RCC till now. ESC RCC poses a diagnostic challenge as many eosinophilic/oncocytic renal tumours are included in the differentials. We present a case of ESC RCC with sarcomatoid differentiation in an elderly female without any clinical features of TSC and discuss the differential diagnosis of oncocytic renal tumours.