A case of enteropathy-associated T-cell lymphoma: diagnosis by flow cytometric immunophenotyping and genome analysis using ascitic fluid.

Enteropathy-associated T-cell lymphoma (ETCL) is a primary extranodal T-cell lymphoma arising in the gastrointestinal tract, and is known as a rare and highly aggressive disease with a poor prognosis. The diagnosis of ETCL is usually established by histological examination using resected tumors or biopsy specimens during endoscopic studies. If tumor specimens for histopathological investigation are not available, then such a case might be difficult to accurately diagnose. We report here a case of ETCL which was diagnosed by cytopathology and flow cytometric immunophenotyping using paracentesis fluid without tumor specimens. Immunophenotyping by flow cytometry (FCM) of the ascitic fluid (AF) was invaluable in the final diagnosis of ETCL. Moreover, genetic alterations in the current case were also demonstrated. We emphasize the usefulness of effusion cytology for the expeditious diagnosis of ETCL. In particular, even in cases without tumor specimens, immunophenotyping by FCM using AF can play an important role in the diagnosis of ETCL, and simultaneous genome analysis may be useful to elucidate the biological characteristics of ETCL.