Repeatedly recurring pleomorphic adenoma: a therapeutic challenge

Pleomorphic adenoma (PA) is the most common tumour of the salivary glands, and can recur even after proper surgery. The extent and timing of surgery for recurrent tumours remains controversial, and multiple recurrences pose a special challenge. We evaluated all recurrent PAs (RPAs) treated at the Helsinki University Hospital through 2004-2013 focusing on patients with multiple recurrences. Follow-up data were obtained until January 2018. Of the 47 patients, 70% were women and the median age was 33.5 years. Most of the RPAs were located in the parotid gland (87%), and six (13%) in the submandibular gland. One-third (17/47) of tumours had been primarily excised. This patient population experienced 75 recurrent events in total with two or more recurrences in 14 patients (30%). The time interval between recurrences shortened after each recurrent event and the tumour was more likely to be multifocal. At the end of the follow-up period, 15% had recurrent disease and malignant transformation had occurred in 6%. Treatment for PA and RPA is challenging and requires centralised management. Patients with RPA are often young and recurrences may cause lifelong morbidity, especially when the tumour recurs repeatedly. The utilisation and timing of postoperative radiotherapy needs to be discussed as well as the potential risk for malignant transformation in this patient population