Micropapillary carcinoma of the urinary bladder: report of a case and review of its cytologic features.

Micropapillary carcinoma (MPC) is an aggressive variant of urothelial carcinoma. MPC has a propensity to invade lymphovascular spaces and detrusor muscle early in the disease that often leads to upstaging and/or lymph node metastasis in many cases at cystectomy. Its association with the usual high-grade urothelial carcinoma provides an easy recognition of malignancy in cytology specimens without attempt at separating or identifying the MPC component. This may be related to our limited familiarity of its cytologic features with only 4 cases described in the literature. We report another case of MPC and highlight its features in cytologic preparations including the presence of singly scattered tumor cells with high nuclear to cytoplasmic ratio and pleomorphic nuclei, clustered cells devoid of fibrovascular core (micropapillae), 3-dimensional cell aggregates, cytoplasmic vacuoles, and micropapillae exhibiting some features of low-grade urothelial neoplasm. Appreciation of these features may help facilitate its early diagnosis and hopefully a better outcome for these aggressive tumors.