Differential diagnosis between pleomorphic adenoma and carcinoma ex pleomorphic adenoma: focus on clinical and MR findings.

BACKGROUND: In parotid tumors, preoperative differential diagnosis between pleomorphic adenoma (PA) and carcinoma ex pleomorphic adenoma (CXPA) remains challenging. OBJECTIVES: The present study aimed to evaluate the clinical characteristics of CXPA and PA and to identify factors associated with the differential diagnosis of these conditions. MATERIAL AND METHODS: We reviewed the medical records of 6 CXPA and 127 PA patients treated surgically at our institution between 2008 and 2024. RESULT: Univariate analysis revealed significant differences in spontaneous pain (p = .044), facial nerve palsy (p = .045), and subjective enlargement (p < .01) between the CXPA and PA patients. Magnetic resonance imaging (MRI) revealed that the proportions of masses with ill-defined margins, localization in the deep lobe, and low apparent diffusion coefficient (ADC) were significantly higher in patients with CXPA than in those with PA (p < .01, p = .048, and p < .01, respectively). Multivariate analysis identified that spontaneous pain and masses with ill-defined margins were associated with CXPA (p = .047 and p = .013, respectively). CONCLUSION: Spontaneous pain and masses with ill-defined margins could be suggestive of CXPA rather than PA. Low ADC levels indicate the possibility of CXPA.