Follicular lymphoma is a common type of lymphoproliferative disease of transformed follicular center B cells [1]. Patients with follicular lymphoma generally present with asymptomatic lymphadenopathy. Extranodal involvement is uncommon, especially in primary gastrointestinal (GI) follicular lymphoma which is very rare [1]. Herein, we present a case of primary duodenal follicular lymphoma.

A 76-year-old male presented with melena. He was on hemodialysis for 7 years for chronic renal failure due to hypertension. His hemoglobin levels were 8.5 g/dl (reference range 13–17) and serum ferritin levels were 85 ng/ml (reference range 10–300). A peripheral blood smear showed normocytic normochromic anemia. Esophagogastroduodenoscopy (EGD) revealed hemorrhagic gastritis in the upper body, and there was no active bleeding. Multiple whitish mucosal nodules measuring 3–10 mm in size were observed in the second portion of the duodenum (Fig. 1). Some flat nodular lesions with a size of 15 mm were also observed in the duodenum (Fig. 2). The endoscopic differential diagnosis is duodenal adenomas, Brunner’s gland hyperplasia, lymphangioma, lymphangiectasia, or extra-nodal marginal zone B cell lymphoma.

Figure 1. Endoscopic examination. Multiple 3–10 mm sized whitish nodules in the second part of the duodenum.

Figure 2. Some 15 mm sized flat nodular lesions were also noted in the duodenum.

Pathologic examination revealed nodular expanding small lymphoid aggregates (Fig. 3), predominant small cells with depressed nuclear contours, and partially mixed large vesicular cells (Fig. 4).

Figure 3. Pathologic examination. Nodular expanding small lymphoid aggregates were noted (H&E, ×40).

Figure 4. Predominant small cells with depressed nuclear contours and partially mixed large vesicular cells (black territories) were noted (H&E, ×200).

Immunohistochemistry showed that tumor cells were CD20+, CD10+, BLC2+, BCL6+, and CD3–, supporting the follicular center B cell phenotype. And CD 21+ expanding follicular dendritic cell pattern favored follicular lymphoma (Fig. 5). A low Ki-67 proliferation index indicated a low grade lymphoma. The histopathologic diagnosis was follicular lymphoma. It was detected as positive in a fluorescence in situ hybridization (FISH) study of the IGH/BCL-2 gene arrangement. Bone marrow examination revealed no involvement of lymphoma. There was no systemic involvement of the lymphoma on abdominal computed tomography (CT) and chest CT. FDG-positron emission tomography (PET) showed no hypermetabolic abnormalities other than mild FDG uptake in the duodenum. Therefore, the final diagnosis was primary duodenal follicular lymphoma with low-grade and stage IA according to the Lugano classification system.

Figure 5. Immunohistochemistry (×50). Tumor cells are CD20+, CD10+, BLC2+, BCL6+, CD3–, CD 21+, and have a low Ki-67 proliferation index.

He had end-stage renal failure and cachexia, so safety was a top priority when choosing treatment options. After consultation with the oncologist, radiation therapy was planned.

Follicular lymphoma is a common type of common type of non-Hodgkin lymphoma and generally has an indolent course and good prognosis [1]. On the other hand, primary GI follicular lymphoma that affects the duodenum is very rare, making up only 1–3% of cases [2], and only a few cases have been reported [3,4].

The most frequently involved sites of primary follicular lymphoma are the second part of the duodenum, followed by the jejunum [5]. A typical endoscopic finding is a whitish multinodular mucosal or polypoid lesion of 1–5 mm in size [3]. These lesions can become ulcerated and potentially develop multifocal involvement of the GI tract. In the present case, multiple small whitish nodules were observed in the duodenum, which appeared to be Brunner’s gland hyperplasia. However, nodular lesions with a size of 15 mm were also observed, which was different from Brunner’s gland hyperplasia. Endoscopic biopsy is crucial for diagnosis, and additional immunohistochemical tests are needed if the diagnosis is uncertain. Therefore, if suspicious lesions are observed on endoscopy, an endoscopic biopsy is required.

Most cases have an indolent course, with low-grade (grade 1–2) and low-clinical stages (stage I or II). However, in some cases, it can progress to advanced lymphoma that requires systemic chemotherapy. Treatment options for primary GI follicular lymphoma have been proposed, including surgery, chemotherapy, rituximab, and radiotherapy. However, no agreement has been reached yet. Due to the rarity of the disease and good prognosis, some oncologists choose to treat duodenal follicular lymphoma as a “watch and wait” approach [6]. In 63 patients with primary duodenal follicular lymphoma, no one did not transformed to high grade disease [7]. So the authors argued that a “watch and wait” strategy seemed a wise strategy [7]. Approximately 70% of patients who received surveillance (“watch and wait” strategy) achieved spontaneous remission or stable disease [5]. Only 3 (9%) patients transformed to high-grade lymphoma. In a Japanese multicenter study, male sex and the presence of abdominal symptoms were independently associated with poor survival [8].

In a French multicenter study, a total of 31 patients with primary GI follicular lymphoma, 14 patients were diagnosed incidentally at endoscopy [5]. Others have symptoms such as abdominal pain and dyspepsia.

In conclusion, the patient underwent EGD with melena and was incidentally diagnosed with primary duodenal follicular lymphoma on endoscopy. Due to the underlying disease and old age, he received radiation therapy as a local treatment. Primary GI follicular lymphoma is often found incidentally without symptoms, so it is important to perform a biopsy when endoscopic findings are suspected. Because it is an indolent disease, close follow-up is possible or local radiation therapy is available.

Informed consent was obtained for this case report.

None.

No potential conflict of interest relevant to this article was reported.

Conceptualization: Hyun-Jung Kim, Jeongmin Choi. Investigation: Hyun-Jung Kim, Jeongmin Choi. Writing—original draft: Hyun-Jung Kim, Jeongmin Choi. Writing—review & editing: Hyun-Jung Kim, Jeongmin Choi.