Natural killer-like T-cell lymphoma of the stomach

We report the case of a 69-year-old white woman who developed a natural kil ler (NK)-like T-cell lymphoma involving primarily the stomach. The tumour c onsisted of large and pleomorphic lymphocytes infiltrating the gastric muco sa. Immunohistochemistry performed on paraffin sections showed the neoplast ic cells to be CD3+, CD5-, CD8-, CD43+, CD45RO+, and CD57+. In addition, th ese cells also expressed HLA-DR, granzyme B, and, to a lesser extent, the C D30 activation marker. No pathologic features suggesting Helicobacter pylor i, Epstein-Barr virus infection, or lymphocytic gastritis were found within adjacent normal mucosa. The patient had no previous history of coeliac dis ease, and her serology for H. pylori was negative. Since lymphomas are usua lly considered the neoplastic counterpart of normal lymphocytic subsets, it is possible that in this case the tumour cells originate from a distinct c ytotoxic T-cell population normally present within the gastric mucosa. The pathogenesis of this highly unusual neoplasm, however, remains a mystery.