Micropapillary Urothelial (Transitional Cell) Carcinoma
Definition
- Aggressive subtype of urothelial neoplasm that invades as small clusters of cells
Note
- Usual papillary urothelial carcinoma is covered separately
Diagnostic Criteria
- Any component of micropapillary pattern should be reflected in the diagnosis
- Even small foci are associated with poor prognosis
- Primarily defined by pattern of invasion
- Invasion by small clusters of cells
- Mean width of clusters <4.5 cells across
- Nuclei predominantly peripheral
- Produces rosette like appearance
- Prominent retraction produces spaces around clusters
- Simulates lymphatic involvement, whis is frequently present too
- Frequently multiple clusters in the same retraction space
- Focal intracytoplasmic mucin may be present
- Agressive, permeative invasion is characteristic
- Cancer appears to melt through the muscularis propria
- Frequently little or no stromal response
- Muscularis propria involvement is generally assumed to be present even if not demonstrable in the specimens received
- In such cases, the report should comment on the poor prognosis and high probability of undetected spread
- Cancer appears to melt through the muscularis propria
- Invasion by small clusters of cells
- Cytoplasmic vacuoles common
- Large vacuole with surrounding cells may produce ring forms
- Overlying surface may show usual urothelial carcinoma in situ, papillary carcinoma or micropapillary carcinoma
- Metastases retain the micropapillary pattern
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates: 10/20/12