Salivary glands

Primary salivary gland neoplasms

Benign

Basal cell adenoma



Topic Completed: 8 April 2021

Minor changes: 18 May 2021

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PubMed Search: Basal cell adenoma[TI] salivary gland[TIAB]

Xiaofeng Zhao, M.D., Ph.D.
Shuanzeng (Sam) Wei, M.D., Ph.D.
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Cite this page: Zhao X, Wei S. Basal cell adenoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/salivaryglandsbasalcelladenoma.html. Accessed December 6th, 2021.
Definition / general
  • Benign salivary tumor composed of nests and cords of small basaloid cells with inner ductal epithelial cells
  • First described by Kleinasser and Klein in 1967 (Arch Klin Exp Ohren Nasen Kehlkopfheilkd 1967;189:302)
  • Initially included in the group of monomorphic adenoma (unfavored term) along with canalicular adenoma; in 1991, recognized as an independent entity in the second edition of the Salivary Gland Tumors Classification by the WHO
Essential features
  • Rare benign epithelial tumor of the salivary gland, displaying monomorphic basaloid cells without a myxochondroid component
Terminology
  • Also called monomorphic adenoma, basaloid salivary gland adenoma
  • Membranous adenoma also called dermal analogue tumor
ICD coding
  • ICD-O: 8147/0 - basal cell adenoma
  • ICD-10: D11.9 - benign neoplasm of major salivary gland, unspecified
Epidemiology
Sites
  • > 80% arise in the major salivary glands, mostly parotid gland (mainly in the superficial lobe), followed by the submandibular gland (5%) and 6% in intraoral location with upper lip being the most common site, followed by the buccal mucosa
Pathophysiology
  • Intercalated duct lineage (IDL) could be precursor; IDL, tubular basal cell adenoma (BCA) and nontubular BCA form a continuum of lesions in which IDLs are related closely to tubular BCA (Histopathology 2014;64:880)
  • According to some studies, myoepithelial or intercalated duct lineage might be the origin of BCA (J Maxillofac Oral Surg 2010;9:289)
  • Epithelial tumor cells of pleomorphic adenoma (PA) may form BCA through certain differentiation mechanisms; basal cells of the epithelium of PA possess reserve cell functions, through epithelial - mesenchymal transdifferentiation, forming the predominant basaloid cell population of basal cell adenoma (Auris Nasus Larynx 2006;33:97)
Etiology
  • Etiology and risk factors for BCA are unknown
  • Membranous type basal cell adenomas can associate with Brooke-Spiegler syndrome (multiple familial trichoepithelioma) caused by CYLD mutation (Eur J Dermatol 2004;14:139)
Clinical features
  • Rare, 1 - 2% of epithelial tumors of salivary glands; 2% of benign salivary gland tumors
  • Solitary or part of turban tumor, Brooke-Spiegler syndrome
  • Usually adults, 67% female, mean age 58 years
  • Rarely is congenital and resembles embryoma
  • Almost all arise in parotid gland, with submandibular gland being a distant second
  • Usually appears as a firm and mobile, slow growing, asymptomatic mass
  • Low recurrence rate except for membranous type
  • Rarely transforms into malignancy; more likely if membranous type (4% malignant transformation)
  • Usually some myoepithelial differentiation using immunostains (Arch Pathol Lab Med 2000;124:401)
  • Membranous type may present as multiple nodules; may coexist with dermal cylindromas or trichoepitheliomas
Diagnosis
  • Diagnosis is established by the histological study; generally, biopsy is accepted as the most accurate method to obtain the diagnosis, although some authors advocate for fine needle aspiration if physical access to the tumor is available
Radiology description
Radiology images

Images hosted on other servers:

Basal cell adenoma in left parotid gland

Basal cell adenoma versus pleomorphic adenoma of the parotid gland

Prognostic factors
  • Recurrence rate ~ 2% on average; almost nonexistent for the solid and trabecular - tubular variants
  • Membranous type most commonly associated with recurrence (25 - 37%), likely due to the multicentricity rather than because of true recurrences (Acta Otolaryngol 1998;118:588)
  • Malignant transformation is more common in the membranous type (4%) than in the other types; total parotidectomy rather than superficial parotidectomy is proposed in the membranous type of BCA (J Oral Maxillofac Pathol 2016;20:142, Acta Otolaryngol 1998;118:588)
Case reports
Treatment
  • Excision: surgical resection with a cuff of normal salivary tissue as the main treatment
Gross description
Frozen section description
  • Adequate sectioning including the capsule should be made on frozen section
Microscopic (histologic) description
  • 2 types of tumor cells:
    • Basaloid cells with basal cells or myoepithelial phenotype
    • Luminal cells
  • Fibrocellular stroma can be present
  • 4 histologic patterns: mixture of at least 2 patterns is common (Ellis: Surgical Pathology of the Salivary Glands, 1st Edition, 1991)
    • Solid pattern: most common, basaloid cells are present in the form of solid masses which may show peripheral palisading
    • Trabecular pattern: narrow or broad trabeculae which may get interconnected with each other creating a reticular pattern
    • Tubular pattern: numerous tubules consisting of a central lumen and an outer single layer or double layered lining of cuboidal and basaloid cells is seen; the lumen often contains an eosinophilic secretion / mucin which is PAS positive
    • Membranous types: histologically identical to dermal cylindroma, eosinophilic hyaline membranes separating cell nests; BCA with greater than 50% membranous pattern should be designated as membranous type
  • Cyst formation is common and can be a main histopathologic feature of basal cell adenoma
  • Occasionally has acinar cells, squamous whorls or keratinization
  • No invasion, no perineurial invasion, no chondromyxoid matrix
Microscopic (histologic) images

Contributed by Shuanzeng Wei, M.D., Ph.D.

Solid pattern

Trabecular pattern

Tubular pattern

Membranous type

Virtual slides

Images hosted on other servers:

Basal cell adenoma with oncocytic features

Cytology description
  • Monomorphic basaloid cels with round nuclei and scant cytoplasm (Diagn Cytopathol 2007;35:85)
  • Irregular nests and trabecula, tubular or peripheral palisading architecture
  • Benign mimickers: cellular pleomorphic adenoma (with chondromyxoid stroma) and myoepithelioma
  • Malignant mimickers: basal cell adenocarcinoma and basaloid squamous cell carcinoma (with significant cytological atypia, mitosis and necrosis) (Am J Clin Pathol 2002;118:S100)
  • Membranous basal cell adenoma simulates adenoid cystic carcinoma (J Cytol 2018;35:55)
Cytology images

Contributed by Shuanzeng Wei, M.D., Ph.D.

Diff-Quik stain

Pap stain

Membranous type Pap stain

Positive stains
Electron microscopy description
Molecular / cytogenetics description
Sample pathology report
  • Parotid, left, parotidectomy:
    • Basal cell adenoma, 1.6 cm, membranous type, margins negative for tumor
Differential diagnosis
Board review style question #1

A 56 year old woman presents with a nodule close to the left ear. Imaging reveals a well circumscribed 1.6 cm nodule in parotid gland. Biopsy findings are shown in the picture above. Which of the following statements is true about this entity?

  1. Cystic change is uncommon
  2. Due to the high recurrence rate, total excision is required for all of these neoplasms
  3. It is one of the most common neoplasms in the salivary glands
  4. It occurs more often in younger patients
  5. It can be associated with Brooke-Spiegler syndrome
Board review style answer #1
E. It can be associated with Brooke-Spiegler syndrome. Brooke-Spiegler syndrome is a rare genetic disease characterized as an inherited skin tumor predisposition syndrome presenting with skin appendage tumors (cylindromas, spiradenomas and trichoepitheliomas) and salivary gland tumor. Some patients can have a membranous basal cell adenoma of the salivary gland. It is caused by germline mutations in the CYLD gene (16q12-q13).

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Reference: Basal cell adenoma
Board review style question #2
Which of the following markers is most useful to differentiate tubular / trabecular predominant basal cell adenoma from pleomorphic adenoma?

  1. Beta catenin
  2. Calponin
  3. CMA
  4. p63
  5. S100
Board review style answer #2
A. Beta catenin. Jo et al. reported that nuclear beta catenin staining can be present in 83% of basal cell adenomas. All adenoid cystic carcinomas (0/20) and pleomorphic adenomas (0/20) were negative. 4 of 5 basal cell adenomas had exon 3 CTNNB1 mutations (Am J Surg Pathol 2016;40:1143).

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Reference: Basal cell adenoma
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