CYSTIC RENAL-CELL CARCINOMA - AROSE AS A SIMPLE CYST, RECURRED REPEATEDLY AS A MULTICYSTIC MASS AND FINALLY PRESENTED AS A SOLID MASS

An unusual case of cystic renal cell carcinoma in a 70-year-old Japane se male is reported. He had had a simple renal cyst removed 1 year ago . On presentation the right kidney was surrounded by multiple transluc ent cysts, which varied in size from 1 to 50 mm. The cyst walls were l ined by single-layered cuboidal epithelium. The differential diagnosis included cystic mesothelioma, cystic lymphangioma and multicystic dys plastic kidney. An immunohistochemical and ultrastructural study and f low cytometric analysis of DNA ploidy were performed. The tumor was di fferentiated to such an extent that it was difficult to diagnose as ca rcinoma; however, it recurred repeatedly. Three and a half years after initial presentation the tumor had invaded the ileum with the patholo gical change to be almost solid when viewed grossly and, microscopical ly, showed tubulo-papillary structures in addition to a cystic pattern . The DNA ploidy pattern revealed a near-diploid aneuploid in the earl y specimen and a polyploid aneuploid in the last specimen.