Cytologic features of the nested variant of urothelial carcinoma: a study of seven cases

Abstract

Background: The nested variant of urothelial carcinoma (NVUC) is a recently described rare variant of urothelial carcinoma with deceptively bland morphologic findings, although it does display aggressive behavior. To the authors' knowledge there is no previous report of cytologic findings in urine specimens from patients with NVUC.

Methods: Urine specimens from patients with histologically confirmed NVUC were reviewed. The specimens evaluated included urine specimens obtained concurrently with or up to 1 month preceding the patients' surgical procedure. All the specimens were analyzed for the presence of cells morphologically similar to the NVUC cells observed in the tissue sections. These cells were evaluated for the following parameters: number of neoplastic cells; cellular arrangement; cell size and shape; cell borders; and cytoplasmic, nuclear, and nucleolar features.

Results: Thirteen urine specimens from 7 patients were included in the current study. The authors were able to identify cells that were similar morphologically to the cells present in the nests of NVUC in all cytologic specimens. The neoplastic cells for the most part were medium-sized, round or polygonal, with abundant, dense, slightly granular basophilic cytoplasm and well defined cell borders. The nuclear/cytoplasmic ratio was increased, the nuclear membranes had irregular contours, and the nuclei contained coarse chromatin with occasional prominent nucleoli.

Conclusions: The cytologic features of NVUC are subtle but distinct. A primary diagnosis of NVUC in urine specimens is not recommended in view of the subtleness of the findings. Nonetheless, the presence of cells with the features described earlier should warrant a cystoscopic examination with histologic confirmation in a patient with a previous history of NVUC.