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Lung tumor

Benign tumors

Pleomorphic adenoma


Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 6 January 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Very rare (< 20 cases reported), ages 35-74 years
● Usually in trachea and major bronchi, rarely in distal bronchi

Related entities
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Alveolar adenoma:
● Benign tumor in asymptomatic patients
● Presents as coin lesion, usually in peripheral lung, consisting of small cystic spaces lined by type II pneumocytes and containing fluid
● Interstitial cellular component consists of epithelioid and spindle shaped cells

Bronchial gland adenoma:
● Includes oncocytoma and mucus gland adenoma, a rare, solitary, benign, well-circumscribed, multicystic, predominately exophytic bronchial tumor

Carcinoma ex pleomorphic adenoma:
● Malignant cases arising from pleomorphic adenoma (Am J Clin Pathol 2011;136:793)




Various images

Intracapsular carcinoma ex pleomorphic adenoma:
● Malignant component does not breach the capsule of the parent tumor, no metastatic potential

Papillary adenoma:
● Arises in peripheral lung, composed of type II pneumocytes (Clara cells), TTF1+; rarely has infiltrative features (Virchows Arch 2000;436:289)

Case reports
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● 56 year old woman with incidental lesion (Arch Pathol Lab Med 2003;127:621)

Treatment
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● Surgical excision, but may recur many years later

Gross description
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● Well circumscribed, no capsule, 2-16 cm, gray-white cut surface, may have tumor tongues outside circumscribed margin

Micro description
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● Nests and trabeculae of epithelial cells in chondromyxoid stroma
● Mixture of epithelial cells with small branching ductules, myoepithelial cells and fibromyxoid stroma with focal hyalinization
● Mild nuclear atypia, occasional multinucleated giant cells, no/rare mitosis
● Lumina may contain PAS+ eosinophilic secretions
● High proliferation index, p16+ (INK4A) (Arch Pathol Lab Med 2003;127:621)

Micro images
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Various images


Metastasizing tumor with benign features

Positive stains
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● Epithelium: CK7, CAM5.2, AE1/AE3, alpha-1-antitrypsin, lysozyme
● Myoepithelial cells: S100, vimentin

Differential diagnosis
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● Primary salivary gland tumors: have ducts with single layer of cells, lack PAS+ material in lumens, no S100+ / vimentin+ myoepithelial layer

End of Lung tumor > Benign tumors > Pleomorphic adenoma


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