Collecting duct carcinoma of the kidney

Abstract

The collecting duct carcinoma that we reported 1 showed tubulopapillary growth pattern and low-grade nuclear atypia (Fuhrman’s grade 2), 2 clearly bordered by fibrous capsule. It was unusual in typical collecting duct carcinoma. Even though it was not mentioned in our paper, the immunohistochemical study showed positive reaction against UEA-1, CAM 5.2, BerEP4 and Progen19. Alcian blue was positive in the aliquot area. More importantly, this small neoplasm (1.5 cm in diameter) existed clearly in the renal medulla. We believed that the tumor color was influenced by the preoperative needle biopsy; therefore, we synthetically diagnosed it as collecting duct carcinoma. In Japan, regular health check-ups among middleaged and elderly people are popular. Therefore, the detection rate of incidental carcinoma may be higher than that in other countries. Subsequently, there is the possibility that the tumors are diagnosed at an early stage, and we may find the clinical and pathological features such as those in our previous paper. Srigley and Eble 3 have proposed major and minor diagnostic criteria for collecting duct carcinoma, and have presented a scheme of the spectrum of collecting duct carcinoma. Papillary carcinomas also show positive reaction for distal nephron markers, which may make it difficult to distinguish between low-grade collecting duct carcinoma and papillary carcinoma. Additional pathologic series should help to elucidate the morphologic and biological spectrum of collecting duct neoplasia. Furthermore, cytogenetic and molecular genetic studies 4–7 may help sort out the morphologic diversity of putative collecting duct carcinomas, very much like the way that molecular studies have assisted in the classification of other renal epithelial neoplasms including clear cell, papillary and chromophobe renal cell carcinomas.