Salivary glands

Primary salivary gland neoplasms

Benign

Basal cell adenoma

Authors: Xiaofeng Zhao, M.D., Ph.D., Shuanzeng (Sam) Wei, M.D., Ph.D.

Editorial Board Member: Bin Xu, M.D., Ph.D.

Deputy Editor-in-Chief: Kelly Magliocca, D.D.S., M.P.H.

Topic Completed: 8 April 2021

Minor changes: 18 May 2021

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

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Table of Contents

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

1 - 3.7% of all salivary gland tumors (Med Oral Patol Oral Cir Bucal 2006;11:E206)
Frequent in elderly adults between fifth and seventh decades; uncommon in young adults (J Dent (Shiraz) 2015;16:291)
Female predilection (2:1) except for the membranous type, which bears an equal M:F distribution (J Laryngol Otol 1989;103:756)
Membranous type basal cell adenomas can associate with Brooke-Spiegler syndrome (Eur J Dermatol 2004;14:139)

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

Nonspecific
Oval to round tumor with smooth distinct margin and high incidence of internal macro or microcysts
Soft tissue components with relative high attenuation on unenhanced CT and enhance well on contrast enhanced CT (AJR Am J Roentgenol 2007;189:W254, AJNR Am J Neuroradiol 2012;33:434)
Relatively homogenous signal intensity of the solid portion; tumor capsule is low signal intensity on T2 weighted images (Dentomaxillofac Radiol 2010;39:349)

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

22 year old man with cytological diagnosis of basal cell adenoma (J Oral Maxillofac Pathol 2015;19:106)
43 year old woman with basal cell adenoma of sublingual gland (Ann Otol Rhinol Laryngol 2003;112:1066)
51 year old man with 6 cm parotic mass of 8 years' duration (Case #375)
54 year old woman with basal cell adenoma extending to skull base and mastoid (World J Clin Cases 2019;7:1351)
55 year old woman with basal cell adenoma of palate (J Dent (Shiraz) 2015;16:291)
59 year old Japanese man with basal cell adenoma of upper lip (Case Rep Med 2014;2014:795356)
65 year old woman with bilateral parotid basal cell adenoma (J Oral Maxillofac Surg 2010;68:179)
19 cases of basal cell adenoma with cribriform pattern (Ann Diagn Pathol 2014;18:5)

Treatment

Excision: surgical resection with a cuff of normal salivary tissue as the main treatment

Gross description

Small (mostly < 5 cm), round or oval, encapsulated nodule (Br J Radiol 2005;78:642)
Membranous subtype often nonencapsulated, multicentric and multilobular (Pilch: Head and Neck Surgical Pathology, 1st Edition, 2001)
Usually brownish appearance; typically uniform and solid, without necrosis; can be cystic (Arch Otolaryngol 1974;99:84)

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

Ductal cells: keratin, alpha-1-antichymotrypsin, CEA, EMA, CD117 (Pathol Res Pract 1991;187:145)
Basaloid cells: vimentin, actin, calponin, S100, p63, GFAP
Spindle cell in the stroma is positive for S100, negative for p63
Can be positive for BCL2 and nuclear beta catenin (Am J Surg Pathol 2016;40:1143)

Electron microscopy description

Myoepithelial cells show microfilaments, desmosomes, junctional complexes, reduplicated basal lamina (Dardick: Salivary Gland Tumor Pathology, 1st Edition, 1996)
Ductal cells show microvilli, tight junctions, desmosomes (Acta Otorhinolaryngol Ital 2005;25:150)

Molecular / cytogenetics description

CTNNB1 mutations are common in BCA, especially those with tubular or tubulotrabecular patterns (Am J Surg Pathol 2016;40:1143)
CYLD1 mutations and loss in sporadic and Brooke-Spiegler syndrome associated basal cell adenoma (Mod Pathol 2018;31:1064, Am J Surg Pathol 2002;26:778)

Sample pathology report

Parotid, left, parotidectomy:
- Basal cell adenoma, 1.6 cm, membranous type, margins negative for tumor

Differential diagnosis

Adenoid cystic carcinoma:
- Infiltrative growth pattern, perineural invasion
Basal cell adenocarcinoma:
- Invasive growth pattern
Pleomorphic adenoma:
- Chondromyxoid stroma blended with epithelial cells, BCA with prominent myoepithelial derived stroma and stroma in BCA does not blend into the epithelial nests
Canalicular adenoma:
- Double columns of cells forming anastomosing canaliculi with paucicellular stroma

Additional references

El-Naggar: WHO Classfication of Head and Neck Tumours, 4th Edition, 2017, Wenig: Atlas of Head and Neck Pathology (Atlas of Surgical Pathology), 3rd Edition, 2015

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?

Cystic change is uncommon
Due to the high recurrence rate, total excision is required for all of these neoplasms
It is one of the most common neoplasms in the salivary glands
It occurs more often in younger patients
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).

Comment Here

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?

Beta catenin
Calponin
CMA
p63
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).

Comment Here

Reference: Basal cell adenoma