Investigation of Sonographic Criteria for Reliable Identification of T1-T2 Low-Grade Malignant Tumors of the Parotid Gland.

The aim of this study was to investigate sonographic findings of low-grade malignant tumors of the parotid gland. The sonographic findings of all patients treated for T1-T2 low-grade carcinomas of the parotid gland between 2003 and 2018 were retrospectively examined and compared with those of patients with pleomorphic adenomas for the following parameters: definition of tumor margins, echotexture, echogenicity, shape and vascularization. Statistical analysis was performed using the χ2 test. A p value of <0.05 was considered statistically significant. A total of 310 patients (62 with T1-T2 low-grade malignant tumors, 248 with pleomorphic adenomas) were evaluated. Our analysis detected a statistically significant difference in the definition of margins, echotexture, echogenicity and shape. Furthermore, we could detect a specific pattern (anechoic islets in a small hypoechoic lesion with distal enhancement) appearing far more frequently in low-grade malignant lesions. It seems that there is still potential to reduce the incidence of the false working hypothesis "benign lesion" on imaging of low-grade malignant tumors.