Primary gastric natural killer/T-cell lymphoma with diffuse CD30 expression and without CD56 expression: A case report.

The majority of natural killer (NK)/T-cell lymphomas occur in the nasal cavity and rarely involve the stomach. They possess a specific immunophenotype, with the expression of cluster of differentiation (CD)56, CD2 and CD3ε, but without CD3 expression. Few cases of NK/T-cell lymphoma have partial CD30 expression. The present study reveals a unique case of a 41-year-old female patient with gastric NK/T-cell lymphoma that did not express CD56 and diffusely expressed CD30. Immunohistochemical staining demonstrated that the tumor cells expressed CD3ε, CD43, CD30 and granzyme B and did not express CD2, CD4, CD5, CD7, CD8, CD56, anaplastic lymphoma kinase, CD20, paired box-5 or pan cytokeratin. Based on the immunostaining profile and morphological features, the initial diagnosis considered was gastric anaplastic large cell lymphoma. However, following a consultation with other pathologists, the Epstein-Barr virus (EBV) status of the patient was investigated to exclude a diagnosis of NK/T-cell lymphoma. Notably, the signal for EBV RNA was diffuse positive. Therefore, the final diagnosis was corrected to NK/T-cell lymphoma. To the best of our knowledge, the present study is the first to report NK/T-cell lymphoma in the stomach with a diffuse CD30-positive and CD56-negative phenotype.