HIGH-GRADE UROTHELIAL CARCINOMA WITH PLASMACYTOID, MICROPAPILLARY AND GLANDULAR DIFFERENTIATION.
This tumor is a poorly differentiated invasive carcinoma, which shows glandular and divergent patterns of differentiation. There is no discrete papillary urothelial carcinoma component or urothelial carcinoma in situ. The tumor shows undifferentiated plasmacytoid histology, glandular differentiation and solid sheet-like architecture (similar to high-grade urothelial carcinoma). Because of the divergent differentiations, the possibility of a metastasis from a primary (like breast or stomach) was considered but was clinically unlikely (with negative mammography and endoscopy). The immunohistochemical profile with the positivity of CK7 and CK20 supports the urothelial origin of this tumor.
A micropapillary variant of transitional cell carcinoma (TCC) was first described in 1994 by Amin et al (1). Four morphological features were described as being distinct to this variant. First, the variant was characterized by a filiform architecture. Second, psammoma bodies, a feature of papillary serous carcinoma of the ovary, were conspicuously absent. Third, the tumor cells were predominantly aggregated in lacunae at random intervals within the tissue. Finally, all cases with the micropapillary component showed at least focal vascular invasion. Their study concluded that the presence of a micropapillary component in transitional carcinoma is associated with high-grade and high-stage TCC.
Even though the tumor in our case has some features of the micropapillary variant of TCC, there is no filiform architecture on the surface component and no vascular invasion is identified. Dr. Amin himself was consulted on this case and he didn't favor this to be a micropapillary variant TCC.
Isolated reports (2,3,4) have described bladder tumors composed of cells that resemble plasma cells by light microscopy but are strongly positive for cytokeratin markers and negative for plasma cell markers by immunohistochemistry.
In conclusion, this case illustrates the varying possibilities of differentiation of urothelial (transitional) cell carcinoma and shows the significance of using immunohistochemistry to establish the cell of origin for these diverse tumors.
Contributed by Muammar Arida, MD and Drazen Jukic, MD, PhD