Parotid gland tumors: comparison of conventional and diffusion-weighted MRI findings with histopathological results

Dentomaxillofac Radiol. 2021 May 1;50(4):20200391. doi: 10.1259/dmfr.20200391. Epub 2020 Dec 11.

Abstract

Objectives: The aim of this study was to investigate the relationship between pathological classification of parotid gland tumors and conventional MRI - diffusion-weighted imaging findings and also contribute the possible effect of apparent diffusion coefficient (ADC) to diagnosis.

Methods: 60 patients with parotid masses diagnosed using histopathology and/or cytology were enrolled in this retrospective study. All patients were evaluated using a 1.5 T MRI. Demographic features, conventional MRI findings, and ADC values (mean, minimum, maximum, and relative) were recorded. MRI findings and ADC values were compared between benign-malignant groups and pleomorphic adenoma vs Warthin's tumor groups.

Results: 60 tumors (48 benign, 12 malignant) were evaluated in a total of 60 patients (39 males, 21 females). The mean age was 59 (±14, 18-86) years old; the mean lesion size was 26 (±10, 11-61) mm. On the texture of conventional MRI, T2 dominantly hyperintense/with hypointensity signal was seen in 87% of pleomorphic adenomas and T2 dominantly hypointense/with hyperintesity signal was encountered in 64% of all Warthin's tumors. Seven (28%) Warthin's tumors were misdiagnosed as pleomorphic adenomas and two others (8%) as malignant tumors. The commonly used mean ADC value was 1.6 ± 0.6 × 10-3 mm2 s-1 for benign tumors, 0.8 ± 0.3 × 10-3 mm2 s-1 for malign tumors, 1 (0.9-1.8) × 10-3 mm2 s-1 for Warthin's tumors, and 1.9 ± 0.3 × 10-3 mm2 s-1 for pleomorphic adenomas. There was a statistically significant difference in ADC values between benign-malignant tumors and pleomorphic adenomas-Warthin's tumors.

Conclusions: Warthin's tumor may occasionally be misdiagnosed as pleomorphic adenoma and malignant tumor because of variable morphologic features. In addition to benign-malignant differentiation, the added ADC measurement may also be useful for differentiating Warthin's tumors from pleomorphic adenomas.

Keywords: Apparent diffusion coefficient; Diffusion-weighted imaging; Magnetic resonance imaging; Parotid gland tumors; Salivary gland.

MeSH terms

  • Adenolymphoma* / diagnostic imaging
  • Adenoma, Pleomorphic* / diagnostic imaging
  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Diagnosis, Differential
  • Female
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Parotid Gland
  • Parotid Neoplasms* / diagnostic imaging
  • Retrospective Studies
  • Young Adult