Role of Cross-sectional Imaging in Evaluation of Parotid Gland Tumours: A Pictorial Review

Radiological evaluation of the parotid gland neoplasms is a major challenge for radiologists, due to the wide variety of imaging features and differential diagnosis. Though Ultrasonography (USG) combined with guided Fine Needle Aspiration Cytology (FNAC) is the primary diagnostic modality, Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) play an important role in the evaluation of patients presenting with suspected neoplastic lesions of the parotid gland. Cross-sectional imaging data of seven patients were selected and reviewed in detail. CT and MRI imaging had been done on patients referred to Radiology Department for clinically suspected parotid tumours. All of them underwent surgical excision and histopathological examination postimaging. Benign tumours usually arise from superficial lobe and exhibit strong signal intensity on T2 weighted images with well-defined margins. Lobulated margins with T2 dark rim are characteristic of pleomorphic adenoma. Hyperdense lesion with cystic changes with occasional bilateralism favour Warthin’s tumour. Most of the malignant parotid tumours involve deep lobe and appear as low signal lesion on T2 weighted imaging with ill-defined margins. Locally aggressive features like subcutaneous/deep infiltration strongly suggests malignancy. Cross-sectional imaging feature of carcinoma ex pleomorphic adenoma is variable from focally aggressive to totally aggressive tumourigenesis. Few malignant tumours like high-grade Mucoepidermoid Carcinoma (MEC) and Adenoid Cystic Carcinoma (AdCC) can show tendency towards perineural spread. Although histopathological examination is required for definitive diagnosis, few pathology-specific imaging findings on cross-sectional imaging can help in localising and characterising the parotid lesions and categorising innocuous benign from sinister malignant lesions and thus narrow down the differential diagnosis.