Recurrent pleomorphic adenoma of the parotid gland: A comparison of radiographic and pathologic tumor burden.

PURPOSE: To compare recurrent pleomorphic adenoma tumor burden as detected on magnetic resonance and computerized tomography imaging with postoperative histopathology. MATERIALS AND METHODS: 44 patients were identified at a tertiary medical center between 2000 and 2015. Patients were included if they had viewable preoperative imaging and a postoperative diagnosis of recurrent pleomorphic adenoma. Primary outcomes were differences in the number and size of lesions detected on imaging and pathology. RESULTS: The size in greatest dimension between pathology and imaging was not significant on aggregate MRI + CT (p = 0.78), MRI (p = 0.41), or CT (p = 0.69). There were more lesions found on pathology compared to both aggregate MRI + CT (p = 0.003) and CT alone (p = 0.014). The number of lesions between MRI and pathology failed to reach significance (p = 0.06). On univariate analysis, the interval between imaging and pathology (recurrent surgery) did not significantly affect the number of lesions detected (p = 0.18). On multivariable analysis, CT as the primary imaging modality and >1 recurrence was independently associated with greater inaccuracy with respect to number of lesions detected (p = 0.006; p = 0.008). CONCLUSION: The size of the largest lesion on pathology can be accurately determined with imaging. Compared to MRI, CT scans significantly underpredict the number of lesions found on pathology. MRI should be prioritized unless contraindications exist. These findings will help guide imaging choice, preoperative planning, and patient counseling.