Primary Intestinal Intraepithelial Natural Killer–like T-Cell Lymphoma: Case Report of a Distinct Clinicopathologic Entity

Abstract Intestinal T-cell lymphoma is a heterogenous group. These tumors differ in their association with enteropathy, intraepithelial or nonintraepithelial origin, primary or secondary involvement, and T-cell or natural killer–like T-cell immunophenotype. There are also nonneoplastic conditions, such as celiac disease, refractory sprue, and reactive T-cell infiltration that mimic intestinal T-cell lymphoma. Therefore, the differential diagnosis requires extensive morphologic, immunophenotypic, and molecular genetic studies. A subset of primary intestinal intraepithelial T-cell lymphoma has emerged in recent years that is distinguished from enteropathy-type T-cell lymphoma in terms of clinical presentation (nonenteropathic), morphology (monomorphic small to medium-sized cells), immunophenotype (CD3−CD8+CD56+), and cytogenetics. We report such a case with a unique immunophenotype (CD3−, cytoplasmic CD3+, CD4−, CD8+, CD5−, CD7+, CD16−, CD56+, CD57−, CD103+, T-cell intracellular antigen 1+, and βF1+) that i...