The background non-neoplastic renal parenchyma may show hyperplastic and papillary neoplastic lesions. Mean age is in the 6th decade. General Gross Description Tumors may affect any region of the kidney. Tumor-parenchymal interface is usually sharp. Large tumors may distort the calyces and pelvis.
Tumor can invade and exit the kidney as renal vein tumor thrombi.
On close scrutiny of the background renal parenchyma, additional seemingly incidental nodules may be found which histologically proves to be papillary epithelial tumors. The tumor cells are cuboidal for the most part but may be columnar. Nuclear cytologic features are variable, usually low grade but may be high grade. Psammoma bodies may be present. Patients may present with costovertebral angle pain, palpable mass and hematuria.