Salivary glands - Basal cell adenoma

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Salivary glands

Epithelial / myoepithelial tumors

Basal cell adenoma

Reviewer: Adriana Handra-Luca, M.D. (see Reviewers page)
Revised: 26 January 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Benign tumor resembling pleomorphic adenoma but with basaloid cells and peripheral palisading
● First described by Kleinasser and Klein in 1967
● Also called monomorphic adenoma; excludes canalicular adenoma

Clinical features
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● 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, 2/3 female, mean age 58 years
● Rarely is congenital and resembles embryoma
● Parotid gland or periparotid lymph nodes
● Low recurrence rate
● Rarely transforms; more likely if dermal analogue variant, (4% malignant transformation)
● Usually some myoepithelial differentiation using immunostains (Arch Pathol Lab Med 2000;124:401)

Treatment
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● Excision

Gross description
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● Encapsulated, often cystic, relatively small

Micro description
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● Solid, trabecular, trabecular-tubular, membranous or tubular growth of epithelial cells (morphological types) resembling pleomorphic adenoma but with peripheral palisading (Mod Pathol 2002;15:298)
● Basaloid cells, bland cytology, occasional peripheral palisading
● Fibrous stroma present
● Occasionally has acinar cells, squamous whorls or keratinization
● No invasion, no mesenchymal component, no perineurial invasion, no myxoid matrix, no cystic change

Micro images
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Various images

Morphologic variants

Calponin+ myoepithelial differentiation

Figure 5A: solid type basal cell adenoma; figure 5B: alpha smooth muscle actin+ myoepithelial cells

Cytology images
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Figure A: basal cell adenoma

Positive stains
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● Ductal cells: keratin, alpha-1-antichymotrypsin, CEA, S100 (alpha subunit)
● Basaloid cells: vimentin, actin, S100 (beta subunit)
● Also IL6 (Hum Pathol 1995;26:501)

Differential diagnosis
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● Adenoid cystic carcinoma
● Basal cell adenocarcinoma
● Pleomorphic adenoma
● Polymorphous low-grade adenocarcinoma

Dermal analogue tumor

General
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● Uncommon subtype of basal cell monomorphic adenoma with clinical and histological resemblance to dermal cylindroma
● First described in 1974 by Drut and in 1977 by Headington and Reingold (Cancer 1977;39:2460, Cancer 1977;40:1702)
● Also called membranous tumor

Clinical features
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● Usually in parotid gland or intranodal parotid gland, ectopic salivary gland in lymph nodes (periparotid, cervical, Cancer 1987;59:1165)
● Sporadic or familial
● Histogenesis: germinal epithelium of ectodermal origin
● Usually men, mean age 60 years old
● 25-38% have cutaneous tumors
● Occasionally coexists with multiple dermal cylindromas (Brooke-Spiegler syndrome, autosomal dominant salivary gland-skin adnexal tumor syndrome, Head Neck 2010;32:684), Warthin tumor
● Multicentricity and multiple recurrencies
● Long period of follow-up required
● Treat with resection, but 25-37% recur, 28% undergo malignant transformation to basaloid adenocarcinoma with destructive infiltrative growth beyond gland margins and perineurial or vascular invasion, but not necessarily pleomorphism, necrosis or mitotic activity

Gross description
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● Usually unencapsulated, 50% multifocal, up to 3.5 cm

Micro description
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● Frequently nonencapsulated
● Jigsaw patterns of epithelial nests surrounded by deposition of basal lamina (thick eosinophilic hyaline basement membrane), resembling dermal eccrine cylindroma (Mod Pathol 2002;15:298) or rarely cutaneous spiradenoma (Hum Pathol 2009;40:1499)
● Two cell types: peripheral small cells with basophilic nuclei and palisading pattern; and large central cells with pale nuclei
● Larger nests may have cystic change and squamous metaplasia; may have oncocytic or sebaceous metaplasia
● May have coalescent membrane droplets within cell nests, malignant change (basal cell adenocarcinoma)
● No infiltration of adjacent parenchyma, nerves, blood vessels

Micro images
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Various images

Jigsaw patterns of basaloid nests

Cytology description
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● Geographic pattern, aggregates of uniform epithelial cells, ill defined cytoplasm, basement membrane-like material (Acta Cytol 2004;48:78, Acta Cytol 1997;41:1015)

Positive stains
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● PAS

Molecular / cytogenetics description
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● 16q12-13 abnormality (cylindromatosis gene, CYLD, Am J Surg Pathol 2002;26:778)

Differential diagnosis
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● Adenoid cystic carcinoma: more cytologic atypia, hyperchromatic angular nuclei or distinct nucleoli; true cribriform pattern with basophilic matrix
● Basal cell adenocarcinoma
● Basal cell adenoma, solid variant: see Acta Otolaryngol 1998;118:588
● Basaloid squamous cell carcinoma
● Canalicular adenoma

End of Salivary glands > Epithelial / myoepithelial tumors > Basal cell adenoma

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