Clinicopathological features and prognosis of 17 cases of duodenal-type follicular lymphoma

Objective: To investigate the clinicopathological features and prognosis of duodenal-type follicular lymphoma (DFL). Methods: The clinical features, endoscopic appearances, pathological features, and treatments of 17 patients with DFL were retrospectively analyzed and followed up. Results: Among the 17 cases of DFL, there were 8 males and 9 females, with a male-to-female ratio of 1∶1.125. The median age was 58 years (33-67 years). Among them, 13 patients with DFL were found in routine physical examination, and most of them showed granular hyperplasia under endoscopy. Among the cases, 15 (88.2%) occurred in the duodenum, and all were located in the descending part of the duodenum. There were 15 cases of single lesions and 2 cases of multiple lesions. Under the microscope, the lesions were located in the mucosal layer or submucosal layer, with a clear or vague “expansive” growth pattern and visible follicular nodules. The nodules were composed of centrocyte-like cells and scattered centroblast-like cells, equivalent to grade 1 or 2 of classical follicular lymphoma. The tumor cells expressed CD20, CD79a, CD10, BCL6, and BCL2. CD21 staining of 9 cases showed that the follicular dendrite network was densely stained around the neoplastic follicles, but lightly stained and sparse in the center. Ki-67 expression was low. Four cases underwent second-generation gene sequencing, among which three cases had detected CREBBP gene mutations. Fourteen cases did not receive any treatment, and disease did not progress. One case underwent local intestinal segment resection without postoperative chemotherapy or radiotherapy and did not relapse. One case received chemotherapy and rituximab treatment, and the lesion completely disappeared. Conclusions: Most of DFL lesions are single lesions with microscopic manifestations similar to those of typical follicular lymphoma grade 1 or grade 2. The special immunophenotype is CD21, which is often more dense and deeply stained around the neoplastic follicles, and has inert biological behavior.