A case of lymphomatoid gastropathy: a self-limited pseudomalignant natural killer (NK)-cell proliferative disease mimicking NK/T-cell lymphomas.

Natural killer (NK)/T-cell lymphomas exhibit aggressive tumor behavior and have a poor prognosis. Recently, self-limited pseudomalignant NK-cell proliferative disorders of the stomach mimicking NK/T-cell lymphomas have been recognized. We report a rare case of lymphomatoid gastropathy in a 71-year-old female. The patient underwent esophagogastroduodenoscopy (EGD) because of slight epigastric discomfort which revealed a 10-mm, reddish, flat elevation with erosion on the posterior wall of the lower gastric body. Histological examination of biopsy specimens showed atypical NK/T cell infiltration with cytoplasmic CD3+, CD4-, CD5-, CD7+, CD8-, CD16-, CD20-, CD56+, CD68-, CD117-, MPO-, TIA1+, and granzyme B+. Epstein-Barr virus-encoded RNA in situ hybridization was negative. Three months later, repeated endoscopic examination surprisingly revealed spontaneous regression of the lesion without any treatment. It is important that endoscopists consider this rare entity in the differential diagnosis, and excessive treatment should be avoided.