A 63-year-old woman with no past history of interest consulted for epigastric discomfort, non-irradiated and unrelated to ingestion, of two months' duration. Physical examination was normal and the only laboratory findings were mild microcytic anaemia and hypogammaglobulinaemia. A gastroscopy was performed, which revealed an excrescent, whitish lesion in the second portion of the duodenum, ulcerated in the centre, friable and with an elastic consistency when biopsies were taken. Pathological examination revealed a dense lymphocytic infiltrate with a centrocytoid habit that destroyed some of the glands and penetrated the epithelium. The immunophenotype of the proliferating cells was CD 20 and CD 43 positive with CD 3, CD 5 and cyclin D1 negative. All this led to confirm the presence of duodenal MALT lymphoma. The patient was referred to the oncology department where the extension study was completed and, after confirming the absence of locoregional and metastatic involvement, treatment with cyclophosphamide was prescribed, with a good response.

