Figure 2. Large B-cell lymphoma with IRF4 rearrangement of the small intestine.
A) H&E 20X demonstrating small intestinal mucosa overlying an atypical lymphoid proliferation. B) H&E 400X demonstrating atypical cells with irregular nuclear contours, coarse chromatin, and variably conspicuous nucleoli. C) >90% of atypical lymphocytes strongly expressed MUM1 (400X). The cells lacked CD10 and BCL2 expression. BCL6 staining failed. D) FISH demonstrated separated red and green probes from the IRF4 gene break-apart probe.