Gastric lymphoma and gastrointestinal stromal tumours (GISTs) are rare malignancies of the upper gastrointestinal tract. The most common gastric lymphoma are low-grade marginal zone B-cell lymphoma (MZBCL) of MALT type. They develop as a consequence of chronic Helicobacter pylori infection, the histological hallmark are lymphoepithelial lesions. In early stages of disease, H. pylori eradication alone may lead to complete lymphoma remission in up to 75% of cases. Nonresponder or locally advanced lymphoma should be treated with radiation therapy. Advanced lymphoma may be treated with the nucleoside analogon cladribine within clinical trials. Based on clinical and novel molecular markers a risk stratification and a prediction of response to therapy might be possible in the future. GISTs are mesenchymal tumours that characteristically express CD-117 (c-kit). They are mostly localized in the upper gastrointestinal tract and are frequently diagnosed in an advanced stage. Conventional chemotherapy is ineffective. For resectable non-metastasized tumours surgical therapy is the treatment of choice. Imatinib is the first and so far only effective systemic therapy which is presently indicated in irresectable or metastasized GISTs. More than 80% of patients respond to imatinib therapy either with partial remission or stable disease. FDG-PET plays an important role in the early prediction of response to imatinib therapy. The optimal dosage and duration of treatment and the role of imatinib as adjuvant or neo-adjuvant therapy for GISTs remains to be defined.
