Clear Cell Sarcoma of Kidney in Adult with Extensive Invasion of Pelvic Veins: Dual Aberration

Clear Cell Sarcoma of Kidney (CCSK) is a highly malignant renal tumour. The mean age of diagnosis is between 12-36 months. Due to heterogeneous histological appearance and age group affection similar to wilms tumour, it often leads to misdiagnosis. It has a tendency to metastasise distantly to bone and its therapeutic response differs from other childhood kidney tumours. So use of Immunohistochemical (IHC) markers becomes essential in many cases in differentiating CCSK from other paediatric renal neoplasms. It is extremely rare in adults, till now only 26 adult cases have been reported in the medical literature. Here, the case of a 49-year-old male presenting with haematuria and pedal oedema is reported. On radiological examination, he had a large left renal mass with tumour extension to Left Renal Vein (LRV) and Inferior Vena Cava (IVC) as thrombi. Histology and Immunohistochemistry (IHC) study revealed CCSK ruling the other differentials. This case is presented for its rarity in adult patients, unusual clinical feature of widespread vascular invasion rather than bone metastasis, simulating Renal Cell Carcinoma (RCC) and aggressive clinical behaviour. The diagnostic challenges faced by pathologist and clinicians further necessitate the proper diagnosis of the tumour for better management of such cases.