Mucosa-associated lymphoid tissue lymphoma in the terminal ileum: A case report

BACKGROUND: The lymphoma of the mucosa-associated lymphoid tissue (MALT) is predominantly found in the stomach. The few cases reported in the literature of MALT lymphomas affecting the ileum are in patients who are already symptomatic and with clear advanced endoscopic findings. We present the first case of an asymptomatic female patient who underwent colonoscopy as a routine examination with the findings of an ulcer in the distal ileum region, which histopathological examination and associated immunohistochemistry revealed the diagnosis of MALT lymphoma. CASE SUMMARY: A 57-year-old asymptomatic female patient underwent a colonoscopy exam for screening. The examination revealed an ulcer of medium depth with well-defined borders covered by a thin layer of fibrin and a halo of hyperemia in the distal ileum portion. Findings are nonspecific but may signal infections by viruses, protozoa, and parasites or inflammatory diseases such as Crohn's disease. Biopsies of the ulcer were taken. The anatomopathological result revealed an atypical diffuse lymphocytic infiltrate of small cells with a characteristic cytoplasmic halo of marginal zone cells. The immunohistochemical study was performed and the results demonstrated a negative neoplastic infiltrate for the expression of cyclin D1 and cytokeratin AE1/AE3 and a positive for BCL60 in the germinal center. The test also revealed CD10 positivity in the glandular epithelium and germinal center of a reactive follicle with dual-labeling of CD20 and CD3 demonstrating the B lymphocyte nature of the neoplastic infiltrate. In BCL2 protein labeling, the neoplastic infiltrate is strongly positive with a negative germinal center. The findings are consistent with immunophenotype B non-Hodgkin's lymphoma, better classified as extranodal MALT. The patient was treated with chemotherapy and showed complete regression of the disease, as evidenced by colonoscopy performed after treatment. CONCLUSION: MALT lymphomas in the terminal ileum are extremely rare and only 4 cases have been reported in the literature. Given the low sensitivity and specificity of endoscopic images in these cases, the pathology can be confused with other important differential diagnoses such as inflammatory diseases or infectious diseases and which makes the biopsy important, even in asymptomatic patients, paired with anatomopathological analysis and immunohistochemistry which is the gold standard for correct diagnosis.