Plasmacytoma : Large Bowel
Higher magnification shows plasmacytic differentiation in the tumor cells - consisting of vesicular nuclei, abundant pink cytoplasm, and pale perinuclear zones. Distinction of cases with this morphology from immunoblastic or plasmablastic large cell lymphoma can be challenging. The immunohistochemical profile in this case was as follows: positive for CD138, kappa light chains, CD45 (weak, focal); negative for CD19 & CD20. Serum protein electrophoresis showed IgA kappa M component.