Ileal mucosa-associated lymphoid tissue lymphoma presenting with small bowel obstruction: a case report

Abstract

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT Lymphoma) of the gastrointestinal tract commonly involves the stomach in the setting of concurrent Helicobacter pylori (H. pylori) infection. Primary ileal MALT lymphoma is rare, and has not been associated with a specific infectious disease. We report a case of a 58-year-old man who presented to the emergency department with constipation and abdominal distension, and signs of an obstructing mass on computed tomography scan. A small bowel resection was performed which revealed an 8 cm saccular dilatation with thickened bowel wall and subjacent thickened tan-yellow tissue extending into the mesentery. Histologically, there was a diffuse lymphoid infiltrate consisting of small atypical cells with monocytoid features. These cells were CD20-positive B-lymphocytes that co-expressed BCL-2 and were negative for CD5, CD10, CD43, and cyclin D1 on immunohistochemical studies. Kappa-restricted plasma cells were also identified by in situ hybridization. The overall proliferation index was low with Ki-67 immunoreactivity in approximately 10 % of cells. No areas suspicious for large cell or high grade transformation were identified. The pathologic findings were diagnostic of an extranodal marginal zone lymphoma involving the ileum, with early involvement of mesenteric lymph nodes. Small hypermetabolic right mesenteric and bilateral hilar lymph nodes were identified by imaging. The bone marrow biopsy showed no evidence of involvement by lymphoma. The patient was clinically considered advanced stage and opted for therapy with rituximab infusions. After six months of therapy, follow-up radiologic studies demonstrated significant decrease in size of the mesenteric lymph nodes.

Fig. 1

a Gross specimen, distal ileum with saccular dilatation. b Gross specimen, ileum, incised to show hemorrhagic mucosa within saccular dilatation

Fig. 2

a Ileal wall with transmural nodular lymphocytic infiltrate. H&E. 20x. b Lymphoplasmacytic infiltrate with monocytoid features. H&E. 200x

Fig. 3

a Lymphocytic infiltrate consists predominantly of CD20 positive B-cells. CD20 immunohistochemical stain. 200x. b B-cells are negative for CD5 which highlights scattered T-cells. CD5 immunohistochemical stain. 200x. c B-cells are predominantly negative for CD10 which highlights few residual germinal center B-cells. CD10 immunohistochemical stain. 200x

Fig. 4

a Clusters of plasma cells located near the mucosal surface. CD138 immunohistochemical stain. 200x. b Plasma cells with predominantly kappa light chain. Kappa in situ hybridization. 200x. c Rare plasma cell with lambda light chain. Lambda in situ hybridization. 200x

Fig. 5

Residual dendritic meshwork identified within lymphocytic infiltrate. CD23 immunohistochemical stain. 100x

Fig. 6

Lymphocytic infiltrate with low proliferation index. Ki-67 immunohistochemical stain. 200x