Carcinoma ex pleomorphic adenoma (CXPA) is a rare, aggressive malignancy arising from pleomorphic adenoma, more commonly found in the parotid gland than in the submandibular gland, with a high risk of recurrence and metastases, particularly to the lungs. Poor prognostic factors include positive or close surgical margins, higher disease stage, and high-grade malignancy. We present the case of a 79-year-old woman with submandibular gland CXPA who underwent resection with a 0 mm margin and pN0 staging, followed by margin extension and selective lymphadenectomy. Computed tomography soon revealed pulmonary metastases; chemotherapy achieved temporary disease stabilization, but local progression necessitated repeat surgery – cytoreductive surgery revealed malignant cells again at the surgical margin. This case highlights the importance of primary radical surgery with negative margins and nodal management. In advanced disease, systemic therapy efficacy is limited.