Micropapillary Variant of Urothelial Carcinoma of the Urinary Bladder: Report of a Case with Cytologic Diagnosis in Urine Specimen

Lee, Young Seok; Lee, Hyunjoo; Choi, Jung Woo; Shin, Bongkyung; Kim, Hankyem; Kim, Insun; Kim, Aeree

Abstract

A micropapillary variant of urothelial carcinoma (MPC) is a distinct entity with an aggressive clinical course. It has a micropapillary configuration resembling that of ovarian papillary serous carcinoma. Its cytologic features have rarely been reported. We report a case of MPC detected by urine cytology. A woman aged 93 years presented with a chief complaint of macroscopic hematuria. Cytology of her voided urine showed clusters of malignant cells in a micropapillary configuration. Each tumor cell had a vacuolated cytoplasm, a high nuclear:cytoplasmic ratio, and irregular hyperchromatic nuclei. An ureteroscopic examination revealed exophytic sessile papillary masses extending from the left lateral wall to the anterolateral wall of the urinary bladder. A transurethral resection of the tumor was carried out. The tumor was characterized by delicate papillae with a thin, well-developed fibrovascular stromal core and numerous secondary micropapillae lined with small cuboidal cells containing uniform low- to intermediate-grade nuclei and occasional intracytoplasmic mucinous inclusions. These tumor cells infiltrated the muscle layers of the bladder, and lymphatic tumor emboli were frequently seen. Recognizing that the presence of MPC components in urinary cytology is important for distinguishing this lesion from low-grade papillary lesions and high-grade urothelial carcinomas can result in early detection and earlier treatment for an improved treatment outcome.