What happened, in summary

This 45-year-old woman had a history of breast cancer 6 years earlier and had been receiving intravenous zoledronic acid, 4 mg every 3 weeks for 18 months. She was referred to oral medicine because of swelling on the left side of the face and submandibular region. The swelling involved a posterior edentulous area of the mandible rather than a typical breast or lymph-node site. Imaging showed an intra-mandibular radiolucent lesion with cortical perforation. Cone-beam CT found a poorly defined 20 x 17 x 14 mm mass in the posterior edentulous left mandible, with expansion and perforation of the buccal cortical plate. The inferior alveolar nerve border was not visible. Because of the aggressive appearance and her breast cancer history, metastasis was strongly suspected, although other jaw lesions were considered. Incisional biopsy showed small nests and individual atypical cells in a collagenized stroma, with marked nuclear atypia and many mitoses. Immunohistochemistry was ER-negative, PR-negative, S100-negative, and LCA-negative, while CK7 and GATA3 were diffusely positive. HER2 showed weak-to-moderate membranous staining in more than 10% of tumor cells. The final diagnosis was high-grade carcinoma consistent with metastatic breast cancer. Oncology referral was arranged, and treatment planning included 17 fractions of head and neck intensity-modulated radiotherapy to a total dose of 60 Gy. After radiotherapy, the mandibular lesion enlarged and caused a lower jaw fracture. Further evaluation showed that the breast cancer had also spread to the lungs and liver. Her condition remained palliative because of widespread metastases, and she died 6 months after the diagnosis of mandibular metastasis.