Peritoneal dissemination of a gastric API2-MALT1-positive MALT lymphoma

The majority of mucosa-associated lymphoid tissue (MALT) lymphomas arises in the stomach but a variety of extranodal sites inside or outside the gastrointestinal (GI) tract can be afflicted.1 Gastric MALT lymphomas most frequently spread to a GI site, MALT lymphomas of extragastric origin rather disseminate to a non-GI site. Moreover, gastric MALT lymphomas disseminate less frequently (up to 25%) than extragastric MALT lymphomas (up to 46%).2 It has been reported that at diagnosis up to a third of all MALT lymphomas have disseminated with involvement of one or multiple MALT-containing organs or non-MALT-containing organs.1 The lymph nodes, bone marrow, spleen and liver are common non-MALT sites but also dissemination to the pleura has been described.3 However, involvement of the peritoneum has not been reported before. A patient with an unremarkable social and family history was referred to us for therapy of a newly diagnosed rectal tumour suspicious for cancer. Staging confirmed a large, obstructing tumour of the middle rectum, which showed high-grade dysplasia and atypical glands suspicious for invasive cancer on histological examination (category 4.3 of the revised Vienna classification). Although, signs of locoregional lymph node metastases were missing, we found multiple small mesenteric lesions and ascites in addition to a thickening of the entire stomach wall (figure 1A) and suspiciously enlarged retrocrural and upper abdominal lymph nodes on a CT scan. Subsequent oesophagogastroduodenoscopy revealed multiple peptic …