Gastrointestinal Follicular Lymphoma: A Single-institutional Experience of 22 Cases With Emphasis on the Comprehensive Clinicopathological Analysis and Diagnostic Re-classification.

ABSTRACT

BACKGROUND/AIM: Distinguishing gastrointestinal involvement in classic follicular lymphoma (CFL) and duodenal-type follicular lymphoma (DFL) is crucial for proper treatment. This study aimed to describe an integrated diagnostic re-classification of gastrointestinal follicular lymphoma (GIFL) and identify useful features for its differential diagnosis. PATIENTS AND METHODS: We reviewed radiological and endoscopic images and pathology slides of 22 GIFL cases, not otherwise specified. RESULTS: Thirteen cases of duodenal grade 1 FL without nodal disease were re-classified as DFL. Five cases of non-duodenal grade 3 FL accompanied by nodal enlargement were re-classified as CFL. The DFL showed peripherally accentuated CD21 immunoreactivity, whereas the CFL showed strong homogeneous CD21 expression. Four atypical cases were re-classified as DFL and CFL in one and three cases, respectively. CONCLUSION: Our findings support the notion that DFL differs from CFL. In cases of GIFL with atypical features, the possibility of gastrointestinal involvement by CFL should be considered. CD21 expression patterns can assist in the differential diagnosis of CFL and DFL.