Basal cell adenoma of parotid gland: two case reports and literature review

Abstract

Most of salivary tumors are benign in nature and are typically diagnosed and classified based on their histopathological presentation. Basal cell adenoma of the salivary glands is a rare, benign disease accounting for 1% to 3% of salivary gland tumors. Despite its low incidence, basal cell adenoma is the third most common benign tumor of the salivary gland after pleomorphic adenoma and Warthin's tumor. It usually appears as a firm and slow-growing mass. Due to the prognosis, differential diagnosis with basal cell adenocarcinoma, adenoid cystic carcinoma and basaloid squamous cell carcinoma is required. In this report, we present two cases; a 62-year-old woman who presented with an asymptomatic, and slow-growing mass and a 64-year-old woman with a static-sized mass in the parotid gland. In both cases, the mass was completely excised, postoperative pathology reports confirmed the diagnosis of basal cell adenoma. We also review the literature and discuss this rare entity.

Keywords: Adenoma; Case reports; Parotid gland; Parotid neoplasms.

Fig. 1.

Preoperative enhanced computed tomography of case 1 patient with asymptomatic mass on the left cheek gradually increasing in size. The left one (4 years ago) shows a well-defined, homogeneous mass (yellow arrow) in the left parotid gland and a slightly larger mass with focal enhancement was observed in the right one (recently).

Fig. 2.

Intraoperative clinical photograph of the mass (yellow arrow) and parotid gland. On gross examination, a round, well-circumscribed, solid mass without necrosis was observed.

Fig. 3.

Intraoperative clinical photograph after total parotidectomy. All facial nerve branches were preserved.

Fig. 4.

Hematoxylin and eosin-stained image of the mass (×100). Basaloid cells with numerous tubules and basal cell linings are observed. There was no necrosis or chondromyxoid matrix.

Fig. 5.

Preoperative enhanced magnetic resonance imaging (MRI) of case 2 patient (female/64, mass without size change for 7 years on left cheek, accidentally found on sonography of annual follow-up for thyroid nodules). MRI shows a benign-looking, low-grade soft tissue mass in the anterior portion, located in the superficial lobe of left parotid gland (yellow arrow).

Fig. 6.

Excised mass and superficial lobe of parotid gland (piece meal).

Fig. 7.

Intraoperative clinical photograph after superficial parotidectomy. All facial nerve branches were preserved.

Fig. 8.

Tubular type of basal cell adenoma on immunohistochemistry (×400) showed positive results for β-catenin nuclear staining.