Renal cell carcinoma of lower nephron origin.

Thirty-four renal cell carcinomas, including 4 small tumors localized in the medulla were studied by means of histochemical and immunohistochemical methods using the markers for the lower nephron. Seven tumors had binding sites for soybean and peanut agglutinins and showed positive reactions to monoclonal antibodies to epithelial membrane antigen and cytokeratin. All these markers normally exist in the epithelial cells of distal and collecting tubules. There was no tumor from the thick ascending limb in our materials because of negative reaction to the monoclonal antibody against Tamm-Horsfall protein. Also negative was to CEA, which means there was no adenocarcinoma of colonic metaplastic origin from the renal pelvic mucosa. There were two histologically different types of cancers derived from the lower nephron, papillotubular adenocarcinoma with partial transitional differentiation, and papillary adenocarcinoma. All seven patients were males, aged between 30 and 84 years. The prognosis was quite poor since all six patients with known follow-up died of tumor.