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.