Primary Mucinous Adenocarcinoma of the Renal Pelvis: A Case Report

Mucinous adenocarcinomas of the upper urinary tract are extremely rare, and the majority of information available comes from case reports or short case series. Intestinal metaplasia is considered a premalignant condition in carcinogenesis. Here we present a case of a 55 -year -old male who presented with a left flank mass extending to the left hemiabdomen and macroscopic hematuria. Pathologic findings revealed that the kidney was transformed into a multiloculated cystic mass measuring 18 x 12 x 11 cm, with a dilated pelvicalyceal system obstructed by a stone at the renal hilus and filled with a gray, soft, gelatinous material. Histopathologic sections showed glandular metaplasia of the proximal ureter ascending to the renal pelvis, lined by intestinal -type columnar epithelium containing goblet cells admixed with malignant glands floating in abundant extracellular mucin, along with poorly differentiated areas composed of signet ring cells. Immunohistochemistry studies showed positive periodic acid Schiff (PAS)/periodic acid Schiff -diastase (PASD), consistent with the mucinous nature of the intracellular and extracellular materials. Positive immunohistochemical staining for CK7, CK20, and CDX2 (CK7+/CK20+/CDX2+) highlighted the intestinal differentiation of this neoplasm. This offers evidence for the intestinal metaplasia-dysplasia-carcinoma sequence rather than a teratomatous or coelomic epithelial origin in mucinous ovarian -like cystadenocarcinoma involving the renal pelvis.