Application of ultrasound in distinguishing the incipient microtumor from inherent lymph nodes of the parotid glands

Abstract

Parotid microtumors (size ≤ 1cm) pose a significant clinical challenge due to their malignant potential and risks associated with surgery. It is imperative to explore the diagnostic workflow that incorporates ultrasound (US) in order to make appropriate clinical decisions with minimal invasiveness. The patients receiving both US and ultrasound-guided fine needle aspiration (USFNA) for the parotid microtumors in a medical center were retrospectively recruited. The ultrasonic features, cytology of USFNA, and final surgical pathology were analyzed to differentiate the tumor origins and their malignant potential. From August 2009 to March 2016, a total of 92 patients were enrolled in the study. The short axis, long-to-short axis ratio, and presence of an echogenic hilum were found to be significantly useful in distinguishing lymphoid tissue origin from salivary gland origin, which was confirmed by USFNA. An irregular border was predictive for malignant parotid microtumors from both origins. Intra-tumoral heterogeneity was also identified as a significant feature associated with malignant lymph nodes. USFNA was able to confirm all malignant lymph nodes, but it had a false negative rate of 8.5% in parotid microtumors of salivary gland origin. Based on the analysis of US and USFNA results, a diagnostic workflow for parotid microtumors was proposed. US and USFNA can be helpful in classifying the origins of parotid microtumors. US-FNA carries the risk of producing false negative results specifically for microtumors originating from salivary glands, but not lymphoid tissue. The diagnostic workflow, which incorporates both US and USFNA, assists in determining the clinical decision for diagnosing and managing parotid microtumors.