Abstract
ObjectiveFine needle aspiration cytology (FNAC) for diagnosis of a parotid gland tumor is widely used but its sensitivity is low and non-diagnostic rate is relatively high. In contrast, core needle biopsy (CNB) has a higher sensitivity and lower rate of sampling errors but has a higher risk of injury to adjacent organs such as facial nerve than FNAC. Screening of patients with parotid gland tumors to identify cases of pleomorphic adenoma (PA) and Warthin tumor (WT) may allow CNB to be confined to patients without PA and WT. We established an algorithm for preoperative diagnosis and management of parotid gland tumor using diffusion-weighted MRI and 99mTc pertechnetate scintigraphy. This algorithm was developed with the goal of maximal reduction of the number of patients in whom CNB is required. The purpose of the study is to validate our algorithm prospectively.MethodsA prospective study was conducted in 71 cases who were newly diagnosed with parotid gland tumor and 53 cases were enrolled in the study. In the algorithm, PA (high apparent diffusion coefficient (ADC) mean≥1.5×10−3 mm2/s) and non-PA (low ADCmean<1.5×10−3 mm2/s) cases are first distinguished based on the ADCmean on diffusion-weighed MRI. Second, among suspected non-PA cases, WT and non-WT are distinguished using technetium-99m pertechnetate scintigraphy. CNB is then performed only in probable non-PA and non-WT cases.ResultsAlthough CNB was only required in 40% (21/53) of all cases, we made a preoperative histopathological diagnosis with an accuracy of 87% (46/53) and we correctly diagnosed whether a tumor was benign or malignant with an accuracy of 96% (51/53). Preoperative surgical planning had to be changed during surgery in only one case (2%)ConclusionsOur algorithm is valuable in terms of clinical practice with highly potential for preoperative diagnosis and with less risk of CNB procedure.
Highlights
Surgical excision of a parotid gland tumor has a risk of facial nerve injury
Core needle biopsy (CNB) was only required in 40% (21/53) of all cases, we made a preoperative histopathological diagnosis with an accuracy of 87% (46/53) and we correctly diagnosed
No cases of tumor seeding, facial nerve palsy, infection, or hematoma occurred after CNB
Summary
Surgical excision of a parotid gland tumor has a risk of facial nerve injury. an accurate preoperative histopathological diagnosis of a parotid lesion is important in establishing a surgical indication and for preoperative surgical planning. Fine needle aspiration cytology (FNAC) is widely used for diagnosis of a parotid gland lesion and can predict if the lesion is benign or malignant with an accuracy of 81–98%[1] The advantages of this method are well documented [1, 2], but its limitations include low sensitivity (about 80%[3]), compared with its high specificity (about 95%[3]), and a relatively high non-diagnostic rate of about 10% due to sampling errors[3,4,5]. CNB has been reported to be safe with no notable complications, this may be due to the publication bias This risk increases for tumors located in a deep portion of the parotid gland[8]. Malignant tumors comprise only about 20% of all parotid gland tumors, and effective pre-test screening for a malignant parotid gland tumor is required for selection of patients who should undergo CNB
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