Multicenter retrospective analysis of primary small intestinal lymphoma in Japan

Primary small intestinal lymphoma (PSIL) is a rare disease, and its clinical characteristics and prognostic factors remain insufficiently defined because of limited large-scale data.

We conducted a nationwide multicenter retrospective study of 686 patients diagnosed with PSIL between January 2008 and December 2017 at 44 institutions in Japan. Clinical characteristics, histological subtypes, and overall survival were analyzed.

B-cell lymphoma was the predominant immunophenotype (n = 623, 91%), whereas T-cell lymphoma was uncommon (n = 50, 7%). Diffuse large B-cell lymphoma (DLBCL) was the most frequent histological subtype (n = 330, 48%), followed by follicular lymphoma (FL) (n = 224, 33%). Compared with other B-cell lymphomas, FL was more common in women and more frequently involved the jejunum (P < 0.001). The 5-year overall survival rate was significantly higher in patients with B-cell lymphoma than in those with T-cell lymphoma (81% vs. 23%, P < 0.001). Multivariate Cox regression analysis identified age > 60 years and T-cell lymphoma as independent adverse prognostic factors, whereas FL was an independent predictor of favorable overall survival.

This nationwide multicenter analysis delineates the clinicopathological features and survival outcomes of PSIL in Japan. FL represents the second most common subtype after DLBCL and is associated with a favorable prognosis among PSIL subtypes.