Uncharted features of a familiar entity: a case of renal cell carcinoma

Introduction: Renal Cell Carcinoma encompasses over 15 distinct subtypes with unique molecular and histological characteristics making it a huge challenge. The presence of a sarcomatoid and rhabdoid component signifies aggressive behaviour and poor clinical outcomes. We present this case for its uniqueness and the heterogenicity it showcases. Case details: A 39-year-old female comes with complaints of pain and mass per abdomen for 2 months. On ultrasound abdomen, right kidney was bulky measuring10x8cm with irregular lesion in mid and lower pole. Right nephrectomy specimen showed irregular and variegated mass with necrosis noted in mid and lower pole of the kidney displacing the hilar structures. Microscopy revealed atypical cells in solid nests, sheets and occasional tubulo-papillary pattern having clear to eosinophilic cytoplasm, pleomorphic vesicular nuclei and prominent nucleoli. Extensive areas of necrosis, sarcomatoid and rhabdoid differentiation was noted with multinucleated giant cells & lymphovascular invasion. Immunohistochemical study showed retained Fumarate hydratase, AMACR positivity, CD-10 and CK-7 negativity and loss of INI1(SMARC B1) expression.Conclusion: RCC with sarcomatoid and rhabdoid differentiation is a rare entity with adverse prognosis. Accurate diagnosis through a combination of histomorphological and immunohistochemical evaluation is critical to prevent the misdiagnosis of this divergent tumour.