Metastatic Pleomorphic Adenoma: A Systematic Review.

BACKGROUND: Metastatic pleomorphic adenoma (MPA) is a benign-appearing pleomorphic adenoma that spreads to regional and distant sites, such as lymph nodes, lungs, or bones, despite lacking malignant features histologically. METHODS: A systematic review of documented case reports and case series of metastatic pleomorphic adenoma is presented. Searches were conducted across various databases to identify articles published from 1953 to December 2024. The variables included were gender, age, symptoms, type of gland, histological features, molecular studies, type of treatment, and follow-up. RESULTS: Of the 95 cases reported, 58.8% affected females, and 41.1% were males. The average age for MPA was 49.9 years, and the mean size was 2.4 cm. The parotid gland was the most commonly affected, accounting for 75.8% of cases, followed by the submandibular gland with 13.6%. The treatment for the (benign) pleomorphic adenoma was excision with 42.1%, followed by superficial parotidectomy with 28.4%. The average time to MPA was 198 months. Among patients with follow-up, the bone and cervical lymph nodes were the most common sites of metastasis, with rates of 21.88% and 20.31% respectively. 52.7% of the patients were alive, and 8.4% died from the disease. CONCLUSION: MPA is a rare paradoxical entity in which a histologically benign salivary gland tumor exhibits malignant behavior by spreading to regional and distant sites, typically after several recurrences. Diagnosis requires a careful correlation of clinical history, histopathology, and radiographic imaging, including long-term follow-up after the surgery of Pleomorphic adenomas.