Nonspecific FDG uptake in the tongue mimicking the primary tumor in a patient with cancer of unknown primary.

For cancers of the head and neck, the combination of (18)F-fluorodeoxy-glucose positron emission tomography (FDG-PET)/computed tomography (CT) gains wide acceptance, especially if the primary tumor is unknown (CUP). A patient underwent FDG-PET/CT for squamous cell CUP with cervical lymph node metastases. FDG-PET/CT showed uptake in the right side of the tongue, rendering this area a possible location for the primary tumor. However, clinical examination revealed a deviation of the tongue toward the left side indicating affection of the left hypoglossal nerve, causing the increased FDG uptake. This case illustrates the interpretive pitfalls of unspecific FDG uptake in PET/CT imaging of the head and neck.