PET/CT illustration of metastatic breast cancer to the left mandibular foramen.

Mental nerve neuropathy (numb chin/lip syndrome) is a sensory neuropathy presenting with numbness in the distribution of the inferior alveolar nerve/mental nerve (chin and lower lip). This is typically unilateral and can be secondary to dental disease or malignancy. When caused by malignancy, these symptoms can be either an initial presentation of an unsuspected tumor or progressive metastatic disease, both of which would indicate poor prognosis. We describe a 48-year-old female patient with a history of breast cancer who presented with left chin numbness and manifested a metastatic lesion involving the left mandibular foramen on PET/CT and subsequent MRI.