Discussion:

A major change in the fifth edition WHO classification of urinary tumors renamed Clear cell papillary renal cell carcinoma to Clear Cell Papillary tumor due to its indolent nature and its characteristics of both clear cell and papillary RCC. It typically arises in the renal cortex, affecting patients across a broad age range (8-88 years, mean 52.8). Clinically, it is often an incidental imaging finding (80%) but can present with local symptoms (18%) and sometimes occurs in end-stage renal disease.

The etiology is unclear, generally sporadic, though some cases are associated with von Hippel-Lindau (VHL) disease.

Grossly, these tumors are generally unilateral, encapsulated with a mean size of 2 cm. The cut surface can be tan-white, pink-tan, yellow, or red-brown. The tumors have both cystic and solid components and typically lack necrosis, although focal hemorrhage can be present.

Microscopically, the tumor cells are arranged in a papillary architecture with small blunt papillae and focal branching papillae or acini interconnected by fibrovascular stroma. The cells have clear cytoplasm and eccentric nuclei. The nuclei are graded 1 or 2, exhibiting luminal polarization and occasionally detaching from the basal membrane. Lymphovascular invasion, renal sinus invasion, and tumor necrosis are not observed.

Molecularly, it lacks typical genetic changes of Clear Cell and Papillary RCC, instead showing specific chromosomal changes (e.g., monosomy 16, 17, 20) and low mitochondrial DNA.

Treatment is nephrectomy. Prognosis is favorable, with no recurrence or metastasis observed post-resection.