This case report describes a male patient with trismus and generalized muscle weakness as the presenting symptom of disseminated malignancy. Trismus was caused by the presence of multiple small nests of undifferentiated tumor cells between muscle fibers of the masseter muscles as well as of other skeletal muscles. The diagnosis was suggested by increased uptake of 18-fluoro-deoxyglucose on positron emission tomography and subsequent ultrasound exami-nation. The primary tumor was not found on autopsy. The patient was at increased risk for malignancy due to his renal transplantation 16 years before. Schlagwörter: malignancy, positron emission tomography, transplantation, trismus, weakness