Gastric involvement in patients with primary mediastinal large B-cell lymphoma.

Gastric involvement is unusual in primary mediastinal large B-cell lymphoma (PMLBCL), which has not yet been adequately studied. The aim of this retrospective study was to investigate the frequency of gastric involvement in 204 consecutive patients with PMLBCL that presented at 23 hospitals in Greece. Two out of 204 patients (1.0%) had gastric involvement at presentation. The first patient had symptomatic gastric disease manifested as upper gastrointestinal (GI) hemorrhage, which was the presenting symptom (first case reported in the literature). The second patient underwent positron emission tomography/computed tomography (PET/CT) at baseline staging which revealed abnormal gastric uptake. Histological examination revealed discordant lymphomatous involvement (MALT lymphoma, in a 33-year old female). The estimated frequency of gastric involvement by conventional staging was 1/204 (0.49%), but no cases were identified among asymptomatic patients. Among asymptomatic patients who underwent PET/CT at baseline staging, the PET/CT-based frequency of gastric involvement was 7.1%, but lymphomatous gastric involvement was discordant. Finally, the frequency of gastric involvement in primary progressive or relapsed disease was 2.2%. Our study shows that gastric involvement is uncommon but can be seen in different clinical settings at presentation or at progression/relapse of PMLBCL. PET/CT-based staging may provide more accurate information regarding the true incidence of sub-clinical gastric involvement in this entity, but histological confirmation is essential in order to confirm the diagnosis.