Risk factors for carcinoma ex pleomorphic adenoma in patients presenting with recurrence after resection of pleomorphic adenoma.

BACKGROUND: In patients presenting with recurrent pleomorphic adenoma (rPA), clinical evaluation can fail to recognize carcinoma ex PA (cxPA). We aim to identify the risk factors for cxPA. METHODS: This is a single institution retrospective case-control study from 2000 to 2015. CxPA was diagnosed based on surgical pathology. Demographics, clinical, and social histories were collected. RESULTS: A number of 13/106 (12.3%) patients were diagnosed with cxPA, of which only 4/13 (31%) had clinical features suspicious for malignancy. Compared to benign rPA, factors associated with cxPA included age >50 (odds ratio [OR] 6.67, 95% confidence interval [CI]: 1.71-25.98, P < .01), >10 pack-years of smoking history (OR 3.36, 95% CI: 1.01-11.14, P = .04), and the largest tumor being >2 cm on pathology (OR 4.42, 95% CI: 1.14-17.10, P = .03). CONCLUSIONS: In patients presenting with rPA, risk factors for malignant transformation include age >50, significant smoking history, and tumors larger than 2 cm. Clinical signs of malignancy such as rapid growth or pain are not always present.