Synchronous bilateral multifocal basal cell adenomas of the parotid gland-a case report

Abstract

Background: Bilateral parotid gland tumors account for up to 3% of cases. In this group, the vast majority are Warthin's tumors. However, bilateral presentations of other parotid gland tumor entities is also possible, an example of which is a basal cell adenoma (BCA). Bilateral BCA is extremely rare, which could cause misdiagnosing it as a Warthin tumor.

Case presentation: The current study reports the unique case of a 48-year-old woman who presented with a 6-month history of slowly growing masses located bilaterally in the parotid region, surgically treated with 5-year follow-up (no recurrence, normal facial nerve function). Magnetic resonance imaging (MRI) revealed three lesions: two in the superficial and deep lobes of the right parotid gland, and one in the superficial lobe of the left parotid gland. A total parotidectomy with facial nerve preservation was performed on the right side, and superficial parotidectomy on the left side 6 months later. Histopathological examination confirmed that all three tumors were BCAs. Molecular analysis didn't show any strong, potential of unknown clinical significance in the studied sample.

Conclusions: Multifocal bilateral lesions of the parotid gland are usually Warthin tumors. Detailed preoperative diagnostics including MRI and histopathological examination is essential to avoid misdiagnosing BCA and Warthin tumors. To our best knowledge, no case of synchronous bilateral multifocal basal cell adenomas of the parotid gland has been reported in English literature so far.

Keywords: Basal cell adenoma; Bilateral; Case report; Parotid gland; Synchronous.

Fig. 1

Patient with bilateral parotid gland tumors (A—right parotid gland tumor, B—left parotid gland tumor)

Fig. 2

MRI of bilateral multifocal parotid basal-cell adenomas. The examination shows heterogeneous lesions, with central cystic areas, partially with higher protein content and signs of bleeding, and peripheral solid components (A. T1-weighted axial image, B. T2-weighted axial image, C. T2-weighted coronal image and D. T2-weighted fat-saturated axial image). Solid components of the tumours present vivid enhancement post-gadolinium-based contrast agent (E. contrast-enhanced T1-weighted fat-saturated axial image) and the time-intensity curves obtained on the basis of dynamic contrast-enhanced sequence show a continuous uptake of the contrast agent suggestive of adenomas (F). Tumors did not show signs of diffusion restriction with ADC values of approximately 1.48 × 10⁻³ mm.²/s (G. diffusion-weighted axial image, b 1000, H. ADC map)

Fig. 3

Axial T2-weighted MRI image post right total parotidectomy presenting a standard view of the post-operative site with one remaining lesion in the superficial lobe of the left parotid gland

Fig. 4

The tumor is surrounded by a fibrous capsule without evidence of invasion, as is characteristic of adenoma. This tumor shows architecture of basal cell adenoma (membranaceous growth pattern)—typical jigsaw puzzle–like islands of basaloid cells, interspersed by occasional vacuolar or small cystic spaces, the cell islands are sharply demarcated from the stroma (H&E staining, × 10)