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

Abstract

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 is comparable to that of a newly identified subset of intraepithelial T cells. The tumor progressed rapidly and the patient died within 6 months after the onset of the disease. We recommend a large monoclonal antibody panel for the differential diagnosis of this heterogeneous group of T-cell lymphoma.