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.

Basal Cell Adenoma of the Upper Lip: Report of a Rare Case With Literature Review

“…BCA is a rare benign neoplasm of the epithelial salivary glands, constituting 1-2% of all salivary gland tumors [ 14 ]. BCA is generally seen among elderly female patients (mean age of 58 years) and exhibits a site predilection for the major salivary glands, chiefly the parotid gland (80% in the superficial lobe), and the submandibular gland (5%) [ 15 ]. Minor salivary gland involvement is an extremely rare occurrence, and the atypical sites for the origin of BCA from minor salivary glands include the upper lip, palate, buccal mucosa, and lower lip [ 4 , 8 ].…”

“…While immunohistochemistry (IHC) examinations may lack specificity and are somewhat contingent on the histologic subtype of BCA, they can serve as an adjunct in differentiating these tumors [ 19 ]. The salient histopathological characteristics encompass monomorphic basaloid epithelial cell proliferation with a sparse cytoplasm and the lack of a chondromyxoid stromal matrix [ 15 ]. Based on their morphological characteristics, BCAs are divided into four patterns: solid, tubular, trabecular, and membranous, with the solid subtype being the most frequently observed [ 1 , 13 ].…”

“…Diagnosing BCA can be challenging as they mimic other lesions that also feature basaloid cells, such as pleomorphic adenoma (PA), adenoid cystic carcinoma (ACC), and basal cell adenocarcinoma (BCAC) [ 13 , 19 , 20 ]. The presence of a monomorphic basaloid epithelial pattern and lack of chondromyxoid stroma serve as histologic differentiating features between BCA and pleomorphic adenoma [ 1 , 15 , 19 , 21 ]. PA shows strong immunoreactivity for calponin and moderate for Pan CK and SMA indicating myoepithelial cell proliferation.…”

“…The distinction between BCA and BCAC relies on the architectural differences despite the similarity in cellular composition. Unlike BCA, BCAC is a low-grade malignancy that demonstrates a non-encapsulated growth pattern, vascular or perineural invasion, cellular atypia, and increased mitotic activity [ 1 , 4 , 13 , 15 , 19 ]. Proliferative markers like Ki-67 and p63 are often used to confirm the histopathological diagnosis, as a strong positivity for Ki-67 and p63 are diagnostic for malignancy [ 22 ].…”

“…The recurrence rate in BCA is influenced by the histological pattern. While the solid and tubular-trabecular patterns exhibit an almost negligible recurrence rate, the membranous type displays a higher recurrence rate (24-37%), possibly due to its multi-centric nature [ 1 , 4 , 5 , 15 , 19 , 25 ]. Malignant transformation in BCA is infrequent, except in the membranous type, which exhibits a 4% transformation rate [ 5 , 13 , 16 , 18 ].…”