Sarcomatoid variant of urothelial carcinoma: Cytological analysis of three cases.

Sarcomatoid variant of urothelial carcinoma (SV-UC) is characterized by the presence of biphasic malignant neoplastic components exhibiting morphological and/or immunohistochemical evidence of epithelial and mesenchymal differentiation. SV-UC is a rare variant of UC and the cytological features of this tumor have not been well described. In the present study, we analyzed the cytological features of a series of SV-UC cases; 6 voided urine specimens from 3 patients with SV-UC were reviewed. Several characteristic cytological features were revealed: i) tumor cells were abundant in a necrotic background and while single tumor cells were predominant, small clusters of cells were occasionally present; ii) tumor cells were large-sized and round to polygonal in shape with ill-defined cell borders; iii) tumor cells had a high nuclear/cytoplasmic ratio and enlarged round to oval nuclei containing coarse chromatin and occasional nucleoli; and iv) spindle-shaped atypical cells were rarely identified (1/6 specimens). The cytological features of i), ii) and iii) are indistinguishable from those of conventional invasive high-grade UC. We hypothesize that these tumor cells originated from the conventional high-grade UC component of SV-UC as this component is usually present in this type of lesion, particularly on the surface of the tumor. Moreover, the sarcomatoid component of SV-UC is usually present in the deeper portion of the tumor and therefore detection of this component in the voided cytological specimen is low. Although cytodiagnosis of SV-UC is extremely difficult, cytodiagnosis of malignancy may prove possible due to the presence of a conventional UC component.