Rare, uncommon and common parotid tumors: Role of PET-CT and diagnostic imaging (CT, MRI and US) in diagnosis and staging - Correlation with histopathology (a pictorial essay)

Learning Objectives PET/CT has been found to be useful in evaluating common parotid tumors. We present a series of rare, uncommon and common parotid tumors with PET/CT, histopathology and correlative image findings.

Introduction: FDG-PET has been shown to have a significant role in the management of patients with salivary malignant tumors in both initial staging and restaging, particularly in those with high grade salivary gland tumors. Analysis of these PET/CT findings may be of use in potentially differentiating aggressive from non-aggressive histologies (histological grading) and predicting response to therapy. Methods: A retrospective review of findings on PET/CT and diagnostic imaging (CT/MRI) was correlated with findings from gross pathologic specimens and tumor histology. We will elaborate on the clinical presentation, imaging and histopathologic findings. The current and potential future role of PET/CT in the management of parotid tumors will also be discussed. Results: Retrospective review of all parotidectomies done over the last two years and having PET/CT imaging in our institution revealed 11 parotid tumors. Of these tumors 5 were considered rare and demonstrated unique histopathology: - Very rare salivary duct carcinoma - Merkel cell tumor - Metastatic melanoma to the parotid with coexisting Warthin’s tumor - Poorly differentiated adenocarcinoma of the parotid with coexisting pleomorphic adenoma - Parotid adenocarcinoma The remaining tumors were squamous cell cancer (4), Warthin's (1) and metastatic skin cancer (1). Conclusions: A pictorial essay was contructed to demonstrate the PET/CT, correlative diagnostic CT/MRI/US imaging and histopathology of these rare, uncommon and common parotid tumors. These correlative findings enhanced the discussion of the role of PET/CT in diagnosis and clinical management