Fig 1.
Algorithm for preoperative diagnosis and surgical planning for parotid gland tumors.
Fig 2.
Scatter plots of ADCmean for each histopathological category.
The ADC ranges for pleomorphic adenoma, Warthin tumor, other benign tumors, carcinoma, and malignant lymphoma were 1.07 to 2.11 (median: 1.60) × 10−3, 0.78 to 1.27 (0.87) × 10−3, 0.62 to 1.51 (0.93) × 10−3, 0.97 to 1.98 (1.13) × 10−3, and 0.61 to 0.69 (0.69) × 10−3 mm2/sec, respectively.
Table 1.
Patient Characteristics.
Table 2.
Preoperative examination results and histopathological diagnosis, and final histopathological diagnosis for each patient.
Fig 3.
MRI of representative cases with pleomorphic adenoma.
Tumors on the right side are reversed to the left side for easier viewing). Case A showed typical MRI findings of pleomorphic adenoma: homogenous T1 low-intensity, homogenous T2 hyperintensity, well-circumscribed borders, solid contrast enhancement, and a high signal on the ADC map. In contrast, cases B to E had indeterminate imaging features of heterogenous intermediate to low-intensity on T2WI, which overlap with malignant lesions. Note that even such indeterminate cases had a relatively high signal on the ADC map, suggestive of pleomorphic adenoma. Case F showed atypical images of pleomorphic adenoma with homogenous T1 low-intensity, heterogenous T2 intermediate to low-intensity, and a low signal on the ADC map, suggestive of non-pleomorphic adenoma. Cases A to D were classified into group 1, whereas cases E and F were classified into group 3. A: Case 12 (60-year-old man), B: Case 26 (84-year-old woman), C: Case 7 (50-year-old woman), D: Case 32 (44-year-old man), E: Case 48 (61-year-old man), F: Case 25 (61-year-old woman)
Table 3.
Accuracy of preoperative diagnosis based on the algorithm.
Fig 4.
MRI and 99mTc pertechnetate scintigraphy in a representative case of Warthin tumor.
Warthin tumor on the left side of a 60-year-old man (case 14). (A) Axial MRI (white arrowheads) showed heterogenous (low to high) intensity on T1WI, heterogenous (low to intermediate) intensity on T2WI, strong gadolinium enhancement, and a low signal on the ADC map (ADCmean 0.94 × 10−3 mm2/sec). (B) A fusion image (bottom left) and planar scans (bottom middle and right) in 99mTc pertechnetate scintigraphy showed intense uptake (white arrows) in the tumor.
Fig 5.
MRI findings in representative cases with malignant tumor.
(A) Images of a diffuse large B cell lymphoma in the left parotid gland in a 48-year-old man (case 49). Axial MRI (white arrowheads) showed low intensity on T1WI, isointensity on T2WI, strong gadolinium enhancement, and a very low signal on the ADC map (ADCmean 0.69 × 10−3 mm2/sec). (B) Images of basal cell carcinoma in the right parotid gland in a 69-year-old man (case 13). Axial MRI (white arrows) showed low intensity on T1WI, heterogenous (low to moderately high) intensity on T2WI, heterogenous gadolinium enhancement with poorly defined margins, and a low signal on the ADC map (ADCmean 1.13 × 10−3 mm2/sec).