Clinical Challenges - December 2016
What is the most plausible diagnosis and what would be the next step?

The diagnosis

To clarify the diagnosis, endoscopic resection of the smaller lesion was performed and deeper biopsies of the other lesions were taken. Histology revealed lymphoid, centroblast, and centrocyte-like cell proliferation with follicular pattern (Figure D). Immunohistochemically, the follicles stained for bcl-6, CD20, and bcl-2 (Figure E), but not CD3, CD5, CD10, or cyclin D1.

A definitive diagnosis of extranodal multiple polypoid follicular lymphoma (grade 2) of the colon was made. Positron emission tomography and computed tomography were negative for more advanced disease, and a bone marrow biopsy was also normal. The patient is now being treated with a combination chemotherapy using a rituximab-containing regimen and remains asymptomatic.

Follicular lymphoma typically arises in lymph nodes with spleen, liver, and bone marrow involvement. Primary extranodal follicular lymphoma without peripheral lymphadenopathy is very uncommon.1 Follicular lymphoma of the gastrointestinal tract is a low-grade lymphoma, usually presenting in the small intestine and characterized by positive reaction to B-cell markers and bcl-2 on immunohistochemical staining.

Malignant lymphomas of the colon represent about 0.2% of all colonic neoplasms and most frequently are diffuse large B-cell, mucosa-associated lymphoid tissue, and mantle cell lymphomas.2 This phenotypic presentation, as multiple lymphomatous polyposis, has been reported in colon follicular lymphomas but is more typical of mantle cell lymphoma.3 Treatment usually consists of chemotherapy containing rituximab (anti-CD20) and should be decided on a case-by-case basis owing to possible relapse and the often indolent course.1

References

1. Damaj, G., Verkarre, V., Delmer, A. et al. Primary follicular lymphoma of the gastrointestinal tract: A study of 25 cases and a literature review. Ann Oncol. 2003;14:623-9.

2. Muller-Hermelink, H.K., Chott, A., Gascoyne, R.D. et al. B-cell lymphoma of the colon and rectum. In: S.R. Hamilton, L.A. Asltonen, eds. WHO Classification of Tumours. Lyon, France: IARC Press;2001:139-41.

3. Hiraide, T., Shoji, T., Higashi, Y. et al. Extranodal multiple polypoid follicular lymphoma of the sigmoid colon. Gastrointest Endosc. 2011;73(1):182-4.