[Papillary renal cell carcinoma: clinico-pathologic studies of 33 cases].

Objective: To investigate the morphologic features, differential diagnosis, prognosis and histogenesis of papillary renal cell carcinoma (PRCC).
Methods: Tumors composed of at least 50% papillae and > 1 cm in diameter were included in this study. Light microscopic observation, immunohistochemical assay of EMA, CK7, CD10, Vim, 34 beta E12 by tissue chip were performed.
Results: Among 516 cases of renal epithelial tumors 33 cases of PRCC were detected. Grossly, hemorrhage, necrosis and multifocality were commonly seen. Besides typical papillae, inconspicuous papillary patterns, such as trabecular, tubular, micronodular and pseudostratified patterns could be seen. Foam cells and psammoma bodies in stroma, and hemosiderin in tumor cells were characteristic. Tumors were of two major types: basophilic type (n = 10), with small cuboid cell and pale cytoplasm (n = 10), 9 of them were low in Fuhrman grading; eosinophilic type (n = 22) with large columnar cells, rich in eosinophilic cytoplasm, 19 of them were high in Fuhrman grading. The remaining case was of clear cell type. The basophilic tumors were all positive for distal tubule marker EMA/CK7, none for proximal tubule marker CD10, 7 tumors positive for Vim. Eosinophilic tumors were positive for EMA/CK7 (9/22), CD10 (10/22) and Vim (6/22). All the tumors studied were negative for 34 beta E12. Follow-up data were available for 24 cases (mean 37 months) with 3-year survival rate of 64.3%, 5-year survival rate of 50%.
Conclusion: PRCC was a distinct malignant entity with unique pathological features. The prognosis of PRCC was worse than that of chromophobe renal cell carcinoma.