Carcinoma ex Pleomorphic Adenoma With an Epithelial‐Myoepithelial Carcinoma Component in the Submandibular Gland: A Case Report

Background: Carcinoma ex pleomorphic adenoma (CXPA) is an uncommon malignant salivary gland tumor arising from pleomorphic adenoma, whereas epithelial-myoepithelial carcinoma (EMC) is a rare low-grade salivary gland malignancy. CXPA with an EMC component in the submandibular gland is uncommon.
Case Report: A 65-year-old man presented with a painless, firm mass in the left submandibular region and weakness of the left lower lip. Computed tomography and magnetic resonance imaging demonstrated an irregular submandibular mass, and FDG-PET/CT showed increased uptake (maximum standardized uptake value, 9.2). Core biopsy suggested pleomorphic adenoma; however, the clinical and radiological findings strongly indicated malignancy. Incisional biopsy was therefore performed under general anesthesia, with a plan to proceed to definitive treatment if malignancy was confirmed. Intraoperative histopathological examination revealed a malignant salivary gland tumor, and tumor resection with neck dissection was completed during the same procedure. Histopathological examination showed invasive CXPA with an EMC component, accompanied by extracapsular invasion exceeding 6 mm, perineural invasion, and extension into adjacent muscle (pT3N0). Although surgical margins were negative, pulmonary metastases developed 12 months after surgery, followed by suspected pleural dissemination and spinal canal extension. The patient declined further aggressive treatment and died of the disease 48 months after surgery.
Conclusion: This case highlights the importance of integrating clinical, radiological, and pathological findings for accurate diagnosis of salivary gland tumors, particularly when biopsy results are inconsistent with clinical suspicion.