Scattered sarcomatoid urothelial carcinoma cells within MALT lymphoma of the urinary bladder

Recently the author encountered a peculiar tumour of the bladder consisting of the following three components: MALT lymphoma, scattered poorly cohesive sarcomatoid urothelial carcinoma within MALT lymphoma, and surface non-invasive, low-grade conventional urothelial carcinoma (UC) occurring in a 65-year-old female. A low-power view showed MALT. Meticulous observations revealed a small amount of non-invasive, low-grade conventional UC at the surface area. In addition, meticulous observations identified a small number of cytokeratin-positive, poorly cohesive sarcomatoid UC cells scattered within the MALT lymphoma. The MALT lymphoma was typical. Immunohistochemically, the scattered sarcomatoid cells within the MALT lymphoma were positive for various types of CK, EMA, p53 and Ki-67 (LI = 70%). The MALT lymphoma was composed mainly of B-cells (CD10, CD20, CD23, CD79 alpha, kappa-chains and lambda-chain), but T-cells positive for CD3, CD4, CD5, CD43 or CD45RO were seen in a very small number. This scattering sarcomatoid UC within MALT lymphoma of bladder has not been reported.