Clear cell adenocarcinoma of the renal pelvis: an extremely rare neoplasm of the upper urinary tract.

Clear cell adenocarcinoma (CCA) in the urinary tract is a rare neoplasm morphologically identical to the Müllerian counterpart. Clear cell adenocarcinoma is extremely rare in the upper urinary tract. We present a case with CCA of the renal pelvis. Microscopically, the tumor exhibited exophytic growth with predominantly tubulocystic structures, as well as solid and papillary patterns. The neoplastic cells were cuboidal with clear to pale eosinophilic cytoplasm and abundant intracellular and extracellular eosinophilic hyaline globules. By immunohistochemically, the tumor was labeled by cytokeratins and hepatocyte nuclear factor-1β. The patient was still alive without evidence of recurrence in the follow-up period of nineteen months after diagnosis.