Cytological Features of Micropapillary and Plasmacytoid Variants of Urothelial Carcinoma - Expert Commentary

The micropapillary and plasmacytoid variants are rare and aggressive urothelial carcinoma (UC) subtypes. The morphological features of these variants in urine cytology are not well described. A recent study published by Straccia et al. in Diagnostic Cytopathology evaluated the urine cytology of 15 high-grade UC cases with plasmacytoid and micropapillary histology to define their cytomorphological characteristics. The study included six patients with the plasmacytoid variant and nine patients with the micropapillary variant. The cohort included three females and 12 males. The median age was 79 years (range 72-90 years).

The cytological features of the plasmacytoid included large, discohesive, isolated tumor cells with abundant, thick cytoplasm, and eccentrically located, hyperchromatic nuclei with coarse chromatin and inconspicuous nucleoli. The discohesive nature of this tumor is consistent with the known clinical phenotype. The immunohistochemical profile of the plasmacytoid variant was positive for pan-CK, CK7, CK20, and negative for vimentin, LCA, S-100 protein, CD138, and E-cadherin.

The key features of the micropapillary variant were papillary cell clusters arranged in a honeycomb, floral cauliflower pattern with high-grade nuclear features, dense cytoplasm, moderate to severe nuclear atypia. These cases were positive for CK20, CK7, PTEN, MUC1, E-Cadherin, and negative for CDX2, MUC5A, and MUC6.

Recent studies identified key genomic features of both plasmacytoid and micropapillary variants. The current study adds to our understanding of the morphological and phenotypic markers of these aggressive variants.

Written by: Bishoy M. Faltas, MD, Director of Bladder Cancer Research, Englander Institute for Precision Medicine, Weill Cornell Medicine, New York City, New York

Reference: 

1. Straccia, Patrizia, Maurizio Martini, Emilio Sacco, Pier F. Bassi, and Francesco Pierconti. "Cytological features of micropapillary and plasmacytoid variants of urothelial carcinoma." Diagnostic cytopathology 48, no. 2 (2020): 111-117.

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