Invasive micropapillary urothelial carcinoma of the renal pelvis presenting as nonfunctional kidney: A unique presentation and review of the literature.

Abstract: Micropapillary urothelial carcinoma of the renal pelvis is a rare and aggressive variant and poses a diagnostic challenge, especially related to the site and histomorphology of the tumor. A 60-year-old female presented with right pelvic-ureteric junction obstruction and a nonfunctioning right kidney. She underwent a simple right nephrectomy. The microscopy examination revealed a high-grade tumor of the renal pelvis, predominant micropapillary architecture. The tumor infiltrated into the kidney, renal sinus, perinephric fat, adrenal gland, and Gerota's fascia. Extensive lymphovascular and perineural invasions were also noted. On immunohistochemistry, tumor cells were positive for GATA-binding protein 3, cytokeratin 7, and cytokeratin 20, while negative for paired box gene 8, cluster of differentiation 10, mammaglobin, and alpha-methylacyl-CoA racemase. The p63 was positive in the conventional areas and negative in the micropapillary pattern. We reported an additional case of micropapillary urothelial carcinoma of the renal pelvis, literature review, and discussed the differential diagnosis. Immunonegativity of p63 in the micropapillary component was an additional finding.
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