Papillary renal cell carcinoma: a clinicopathologic and immunohistochemical study of 105 tumors.

Papillary renal cell carcinoma is the second most common carcinoma of the renal tubules and has been characterized genetically. Its morphologic features are incompletely characterized. It has been suggested that the presence of cytokeratin 7 is specific for papillary renal cell carcinoma. Collecting duct carcinoma might have papillary architecture, and it has been suggested that reaction with the Ulex europaeus lectin is specific for it. Sections from 105 papillary renal cell carcinomas larger than 12 mm in diameter from 100 patients were studied, and immunohistochemical reactions were performed on 91. The tumors formed two morphologic groups. Type 1 (67 tumors) consisted of papillae and tubular structures covered by small cells with pale cytoplasm and characterized by small oval nuclei with inconspicuous nucleoli, frequent glomeruloid papillae, papillary edema, foamy macrophages in papillary cores, and psammoma bodies. Type 2 (38 tumors) consisted of papillae covered by large cells with abundant eosinophilic cytoplasm and characterized by pseudostratification and large spherical nuclei with prominent nucleoli, glomeruloid papillae, psammoma bodies, edematous papillae, and foamy macrophages in papillary cores are uncommon. Type 2 tumors were larger, more common in patients younger than age 40, and more frequently Stages 3 or 4 than were Type 1 tumors. Pseudocapsules were common in both and often were infiltrated by carcinoma. Sarcomatoid foci were found in five tumors. Eleven were stage T1, 54 T2, 23 T3, and 12 T4. Reaction for cytokeratin 7 was strong or moderate in 48 of 61 Type 1 tumors, and reaction was null in 24 of 30 Type 2 tumors. No tumor reacted with U. europaeus lectin.