Basal Cell Adenoma of the Parotid Gland: Characteristics of 2-phase Helical Computed Tomography and Magnetic Resonance Imaging

Objective: The goal of this study was to report the radiologic characteristics of basal cell adenoma of the parotid gland, which is a relatively rare neoplasm.

Methods: A radiology and otolaryngology specialist reviewed the 2-phase helical computed tomography (CT) (n = 6) and/or magnetic resonance (MR) imaging (n = 2) scans of 7 patients with basal cell adenoma. The authors evaluated the imaging characteristics, including tumor size, location, contour and margin, internal density or signal intensity, contrast enhancement pattern, and presence of calcification. The imaging features were then analyzed and correlated with the pathologic findings.

Results: All the tumors presented as small (less than 3 cm), well-encapsulated, round or oval masses on CT or MR imaging. On the 2-phase CT scan, the mostly solid-looking tumors (n = 4) showed marked contrast enhancement on the early phase, and there was a subsequent decrease in attenuation on the delayed phase. These tumors were classified as the solid subtype on histologic examination. Meanwhile, the tumors with large cystic areas (n = 2) showed gradual and additional enhancement on the delayed phase and were classified as the tubular or trabecular subtype on pathologic evaluation. There were small spots of low attenuation in the tumors of the solid subtype, which were proved to be intratumoral microcysts in the pathologic correlation. Calcification was found in a tumor.

Conclusions: Basal cell adenomas of the parotid gland present as small well-marginated tumors and appear as masses with central large cysts or solid masses with microcysts on CT and MR imaging scans. Basal cell adenomas of the parotid gland had at least 2 different enhancement patterns on the 2-phase helical CT scans, and the enhancement patterns and imaging architecture were related to the histologic subtype of the tumors.