This finding indicates that EBV is not the cause for the NK cell activation and excessive proliferation seen in NKCE and LG and distinguishes these diseases from malignant diseases they can mimic such as extranodal NK/T-cell lymphoma, nasal type. In isolated reports, LG has occurred in individuals with Helicobacter pylori infection of the stomach or a history of stomach cancer, while NKCE has been reported to occur in patients with gluten sensitivity or circulating anti-gliadin antibodies. Both of the latter conditions are associated with the development of GI tract lymphomas. However, the relationship of any of these findings to the etiology of LB and NKCE is unclear. Histology
Biopsies of NKCE tissues reveal atypical medium to large lymphocytes identified by immunohistochemistry to be NK cells that are multiplying at a moderately rapid rate and that lack evidence of being infected by the Epstein-Barr virus. These cells are located primarily in the lamina propria, i.e. loose connective tissue lying just below the epithelium lining the GI tract. There is generally little invasion of these cells into the epithelium, submucosa, or glands of the GI tract, and the lesions almost always show a complete absence of vascular injury due to invasion by these cells. The lesions in LG closely resemble those of NKCE.
Natural killer cell enteropathy, also termed  NK cell enteropathy (NKCE), and a closely related disorder, lymphomatoid gastropathy (LG), are non-malignant diseases in which one type of lymphocyte, the natural killer cell (i.e. NK cell), proliferates excessively in  the gastrointestinal tract (GI tract). This proliferation causes red, sore-like spots, raised lesions, erosions, and ulcers in the mucosal layer surrounding the GI tract lumen. Both disorders cause either no or only vague symptoms of GI tract disturbances such as nausea, vomiting, and bleeding.In 2006, a persistent but apparently benign disease that involved the proliferation of NK cells at multiple sites throughout the intestines was described. This disorder appeared similar to and easily mistaken for a highly malignant disease, extranodal NK/T-cell lymphoma, nasal type. In 2010, a similarly non-malignant disorder that involved the proliferation of NK cells in the stomach was described. The disease mimicked gastrointestinal lymphomas. Since these first descriptions, several case series and case reports have been published on these enteropathies.The two NK cell proliferation diseases have been termed NK cell enteropathy and lymphomatoid gastropathy with NKCE being seen mostly in the United States and Korea and LG being seen mostly in Japan. Besides this geographical difference, the only other critical difference between the two diseases is that the lesions in NKCE occur in the small intestine, colon, stomach, and/or esophagus while those of LG are limited to the stomach.