Microcystic urothelial carcinoma: a case report.

Microcystic urothelial carcinoma (MUC) is a rare variant of urothelial carcinoma that is highly aggressive with poor prognosis. Due to the scarcity of cases, its histologic morphology and immunohistochemical characteristics are still not clear. This paper reports a 71-year old female patient with gross hematuria and abdominal pain. Imaging examination showed that the bladder wall was thickened, and rough. A soft tissue mass was seen in the bladder and the left lower ureter, and the boundary between the bladder and the uterus and bilateral adnexa was not clear. Multiple enlarged lymph nodes were seen around the abdominal aorta and left iliac artery. Cystoscopy showed diffuse thickening and edema of the left wall of the bladder, local rough bleeding, and histopathologic results showed that the lesions were consistent with high-grade invasive urothelial carcinoma. Radical cystectomy and bilateral ovariectomy were performed. By microscopic observation the tumor showed infiltrative growth with cystic structures of different sizes. Mitotic figures were frequent and a large amount of mucus was in the stroma. The same type of cancer was found in the left ovary. Immunohistochemistry showed CK5/6 +, p63 +, Pax-8, MUC5AC, CK7, and Ki67 was 50%. Postoperative pathology confirmed that MUC involved the left ureter with ovarian metastasis. Two months after the operation, the patient died of vascular invasion. Because tumor cells were bland in morphology and had no specific immunohistochemical markers, they were easily missed and misdiagnosed by pathologists. Here, we describe this case and analyze it with relevant literature to deepen understanding of MUC.