Breast cancer is the most common cancer in women and the second leading cause of cancer-related death. Breast cancer manifestations in the head and neck are relatively rare, and they are mostly bony metastasis to the mandible and maxilla. In this paper, we present a case report of a metastatic tumor in the mandibular angle originating from breast carcinoma. A 32-year-old female patient with a paresthesia/anesthesia in the left mandibular area was referred to us to aid in the differential diagnosis between osteonecrosis and metastasis. Her medical history revealed a radical bimastectomy 3 years ago for invasive lobular carcinoma of the breasts. Additionally, she received chemotherapy and radiotherapy 3 years ago, and intravenous zoledronic acid was administered every 3 weeks. Intraoral examination did not reveal any mucosal ulcer or fistula, and there was no radiological evidence of cyst. The patient demonstrated good oral hygiene. Palpable regional left submandibular lymph nodes and a few swellings on the lateral angular mandibular surface were observed. Cone-beam computed tomography (CBCT) and positron emission tomography (PET) were performed. CBCT showed small poorly diffused radiopacity in proximity to the mandibular angle on both medial and lateral surfaces. PET showed fluoro-2-deoxy-D-glucose uptake in the mandible in the left angle surface area. Based on the patient’s clinical history, signs, symptoms, and tomographic evidence, we were able to diagnose mandibular metastasis. This case also highlights the importance of proficiency in reading tomographic examinations, which can be carried out in dental clinics for various purposes. In the absence of symptoms, misdiagnosis can occur, underscoring the significance of accurate interpretation and diagnosis.