This case illustrates prominent mesenteric lymphadenopathy and infiltrates that, although having a background of Crohn disease, are not related to small bowel active inflammation. The findings are too prominent to be attributed to mesenteric panniculitis as well.

Biopsy of one of the nodes was performed:

Macroscopy: Labeled "Mesenteric lymph node biopsy". 5 pieces of yellow/pale tan tissue in aggregate 30 x 20 x 3 mm.

Microscopy: The sections show lymph node and surrounding fibroadipose connective tissue. The node shows an expanded follicular architecture with an extension of follicular structures into surrounding adipose tissue. Within expanded follicles, there is a dual population of small, hyperchromatic, cleaved cells of centrocytic appearance, accompanied by large cells with prominent nucleoli and pale staining chromatin in keeping with centroblasts, the latter numbering fewer than 15 per high-power field.

Immunoreactivity with antibodies against CD20, CD10, Bcl-6 and Bcl-2 is present within the neoplastic follicles.  Ki67 proliferative index within the follicles measures < 10%.  CD21 immunohistochemistry highlights expanded follicular dendritic cell networks. CD3 and CD5 immunohistochemistry highlight an interfollicular T lymphocyte population.  Immunohistochemistry with the following markers is negative:  MUM-1, CD15, CD30, Cyclin D1, TdT, c-myc, CD138.

Conclusion:  Mesenteric lymph node biopsy:  Follicular lymphoma, low-grade.

Although its mechanisms are not completely understood, patients with inflammatory bowel disease are speculated to have an increased risk of malignant lymphomas, particularly the non-Hodgkin form ¹.