Presence of clonal T-cell receptor gene rearrangements provides evidence of widespread intramucosal intestinal T-cell lymphoma.

Intestinal T-cell lymphoma (ITCL) is a rare type of extranodal lymphoma derived from intraepithelial T-cells and generally exhibits macroscopically evident ulcerated lesions of the bowel wall composed of pleomorphic tumor cells. We report immunophenotypic and molecular genetic findings in an unusual small-sized intramucosal type of ITCL observed in a 74-year-old man presenting with enteropathy. Biopsies obtained from duodenum and jejunum showed a conspicuous accumulation of small-sized lymphoid cells forming intraepithelial clusters. The predominantly intraepithelial spread was accompanied by a spilling over to the lamina propria but not to deeper layers of the duodenal and jejunal wall, thus resulting in a purely intramucosal manifestation. This growth pattern and the immunophenotypic profile (CD3+, CD4-, CD8+, CD103+) suggested that the lesion may fall in the spectrum of ITCL. However, since the lymphoid cells cytomorphologically lacked neoplastic features and showed a small growth fraction. a reliable diagnosis of malignant lymphoma could not be established by histological and immunohistochemical methods. In this case a tissue-based polymerase chain reaction (PCR) analysis of T-cell receptor (TCR) beta and gamma gene rearrangements proofed to be essential in confidently distinguishing multifocal monoclonal intramucosal T-cell lymphocytosis from an intense reactive inflammatory infiltrate in celiac disease (CD). Our observation highlights that detection of clonal rearrangements of TCR genes is particularly useful in detecting ITCL composed of cytomorphologically innocuous T-cells because histologic diagnosis in such cases is at best presumptive.