Abstract
Plasmablastic lymphoma (PBL) is a recently identified entity that is considered to be a type of diffuse large B-cell lymphoma with a unique immunophenotype and a predilection for the oral cavity of patients with the human immunodeficiency virus (HIV). Although its clinical features may help in the differential diagnosis, an extraoral location in a patient without HIV makes it more difficult to suspect clinically. This case report is the first to describe a patient with PBL originating from the jejunum in a 60-yr-old, HIV-seronegative man. Computed tomography of the face, chest and abdomen showed about a 9.4 x 9.0 cm mass of the proximal jejunum, multiple masses in the musculoskeletal soft tissue, and multiple lymphadenopathies. The histological examinations demonstrated a large cell lymphoma with plasmablastic differentiation. The neoplastic cells were diffusely positive for MUM1, epithelial membrane antigen and lambda light chains, and focally positive for CD79a; but negative for CD3, CD20, CD30, CD34, CD45RO, CD56, CD99, and CD117. The proliferation index by Ki-67 immunohistochemistry was approximately 70%. These findings were compatible with the diagnosis of PBL. The findings in this case suggest that PBL should be included in the differential diagnosis of a small bowel mass even in a HIV-negative patient.