Primary Extra Renal Papillary Renal Cell Carcinoma Masquerading as A Metastatic Carcinoma: A Unique Case with Dual Malignancies

Abstract

A 50-year-old male presented with abdominal pain, pain during defaecation, constipation, bleeding per rectum for 2 months. Colonoscopy showed an ulcero-proliferative growth, that is 2.5 cm from anal verge. Further PET-CT confirmed the growth in the lower rectum with mesorectal fat stranding and an irregular, lobulated, encapsulated solid-cystic mass in right perinephric fat, separated from the kidney (suggestive of metastasis), with intact bilateral kidneys. Biopsy of the rectum revealed an adenocarcinoma and biopsy of right perinephric mass revealed a papillary neoplasm. Following which abdominoperineal resection with perinephric mass excision was performed, due to encapsulation of mass. Histopathological evaluation and further immunohistochemistry performed was positive for vimentin, AMACR, CD10 and negative for other markers to rule out metastasis of either. This led to the diagnosis of synchronous primaries i.e., Extra-renal papillary renal cell carcinoma and adenocarcinoma of rectum.