Mayur N. Patel1, Hitesh Kumar K. Rajpura2, Rajendra N. Solanki3, Hemant Patel4
BACKGROUND Pleomorphic adenoma of parotid gland shows mild enhancement immediately after IV contrast injection. This property can be used in differentiating it from other parotid neoplasms. The aim of this study was to register the delayed CT enhancement characteristics of pleomorphic adenoma and to compare these results with the enhancement characteristics of other parotid gland tumors. MATERIALS AND METHODS Twenty pathologically proven parotid gland neoplasms were reviewed on preoperative CT scans. Lesions included two cases of Warthin’s tumors, two cases of squamous cell carcinomas, ten cases of pleomorphic adenomas, two cases of acinic cell carcinoma, three cases of mucoepidermoid cancers and one case of metastasis. CT scans were performed after administration of 140 mL of IV contrast at three serial intervals -first immediately after contrast injection, second after 8 minutes & the last one after 24 minutes. The mean normalized Hounsfield unit (HU) attenuation of these lesions was calculated by drawing ROI around the entire mass. This CT HU was divided by that of the contralateral uninvolved parotid gland without changing the location within parotid gland and size of ROI. RESULTS Progressive homogeneous contrast enhancement was detected with time in all pleomorphic adenomas. Mean enhancement within the lesion was 1.25±0.30 at 8 minutes and 2.33±0.60 at 24 minutes. For non-pleomorphic adenomas, degree and pattern of contrast enhancement between the immediate and delayed CT scans remained same. In our study, A multiphasic CT for pleomorphic adenoma and non-pleomorphic adenoma had high sensitivity, specificity, positive and negative predictive values (98.5% vs. 82.5%, 94.5% vs. 97.5%, 90.7% vs. 94.5%, 100% vs. 91.7% respectively). CONCLUSION Pleomorphic adenomas show delayed CT contrast enhancement with an increase in homogeneity with time. This feature is useful in differentiating it from other parotid neoplasms.
