The limitations of gallium scintigraphy in the differentiation between benign and malignant salivary gland mass lesions

The aim of this study was to evaluate the ability of gallium scintigraphy to differentiate between benign and malignant salivary gland mass lesions and to identify what types of lesions surpass its diagnostic utility. By considering the uptake of 67Ga, 193 salivary gland masses were graded visually as negative, weakly positive, moderately positive or strongly positive in comparison to the uptake in the nasal cavity and the liver. The uptake was compared with histopathological findings. Among 39 malignant tumours, uptake was positive in 31 (79%) (strongly positive in 18, moderately positive in seven and weakly positive in six) and uptake was negative in eight (21%). Adenoid cystic carcinoma was the most common malignant tumour in our study (11/39), and uptake was negative in five (45%) of these tumours. Malignant tumours did not differ significantly in size despite differences in uptake. Among 154 benign lesions, uptake was negative in 101 (66%) and positive in 53 (34%) (strongly positive in 12, moderately positive in 19 and weakly positive in 22). Out of 88 pleomorphic adenomas, 41 (47%) showed positive uptake. Sensitivity, specificity and accuracy for gallium study were 80%, 66% and 68%, respectively, when the malignancy criterion was weakly positive uptake. Accuracy was greatest (83%) when the criterion was strongly positive uptake, but this criterion failed to detect more than a half of malignant tumours (46% sensitivity). In conclusion, gallium scintigraphy had limitations in differentiating between benign and malignant salivary gland mass lesions. Adenoid cystic carcinomas and pleomorphic adenomas were the principal sources of false negative and false positive results, respectively.