Lymphomatoid gastropathy: a distinct clinicopathologic entity of self-limited pseudomalignant NK-cell proliferation

Diagnostic errors in distinguishing between malignant and reactive processes can cause serious clinical consequences. We report 10 cases of unrecognized self-limited natural killer–cell proliferation in the stomach, designated as lymphomatoid gastropathy (LyGa). This study included 5 men and 5 women (age, 46-75 years) without any gastric symptoms. Gastroscopy showed elevated lesion(s) (diameter, ∼ 1 cm). Histologically, medium-sized to large atypical cells diffusely infiltrated the lamina propria and, occasionally, the glandular epithelium. The cells were CD2+/−, sCD3−, cCD3+, CD4−, CD5−, CD7+, CD8−, CD16−, CD20−, CD45+, CD56+, CD117−, CD158a−, CD161−, T cell–restricted intracellular antigen-1+, granzyme B+, perforin+, Epstein-Barr early RNA−, T-cell receptor αβ−, and T-cell receptor γδ−. Analysis of the 16 specimens biopsied from 10 patients led to a diagnosis of lymphoma or suspected lymphoma in 11 specimens, gastritis for 1 specimen, adenocarcinoma for 1 specimen, and LyGa or suspected LyGa for 3 specimens. Most lesions underwent self-regression. Three cases relapsed, but none of the patients died. According to conventional histopathologic criteria, LyGa is probably diagnosed as lymphoma, especially as extranodal natural killer/T-cell lymphoma, nasal type. However, LyGa is recognized as a pseudomalignant process because of its clinical characteristics. The concept of LyGa should be well recognized.