The picture given below shows the scintigraphy scan image of the right parotid gland. 99mTcO4− is intravenously administered and a dynamic scan (anteroposterior view) is performed which shows uptake of the radionuclide by the gland [Fig A]. Citric acid is instilled into the oral cavity 20 minutes after the intravenous injection to stimulate the secretion of saliva and a scan is performed which shows incomplete washout of the radionuclide from the gland [Fig B]. Based on the findings, which of the following can be excluded from the differential diagnosis?
Warthin’s tumors and oncocytomas are derived from the epithelial cells of excretory ducts and do not communicate via excretory ducts. Thus, 99mTcO4− is taken up by the solid component of these tumors and is not eliminated after the stimulation of saliva secretion. Whereas, 99mTcO4− is not taken up by pleomorphic adenomas at all.