Biopsies of the gastric body shows a diffuse infiltrate of bland monotonous small lymphoid cells with moderate amount of pink cytoplasm and bland nuclei percolating in the lamina propria without any destructive features.

CD2 and CD3 are both strongly positive. However, CD5 is negative in most of the cells while few scattered background T-cells are positive on CD5. The lack of CD5 allows exclusion of T-cell lineage and supports NK-derivation. NK cells not express CD5 while T-cells do.

CD56 is strongly positive as is typical of most NK-cell proliferations. Additionally CD4 and CD8 were negative while EBV was negative.

PCR for T-cell gene rearrangements were polyclonal consistent with the germline TCR genes expected in NK cell proliferations.

There is involvement of the duodenal biopsies with strong CD56 expression noted.