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Lung tumor

Other Carcinoma

Squamous cell carcinoma


Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 22 January 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Carcinoma arising from squamous epithelial cells, morphologically characterized by proliferation of atypical, often pleomorphic squamous cells; graded as well, moderately, or poorly differentiated; well differentiated carcinomas are usually associated with keratin production and presence of intercellular bridges between adjacent cells; subtypes include basaloid, clear cell type, papillary, small cell nonkeratinizing (WHO)

Terminology
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Early lung carcinoma of hilar type
● Arises proximal to sub segmental bronchi (i.e. major bronchi), confined to bronchial wall with no lymph node metastases
● Usually squamous cell carcinoma; may be polypoid, nodular, superficially infiltrating or mixed
● Longitudinal mucosal folds show changes at tumor border
● Superficial tumor has thickened and fused folds
● Five year survival is 90% or more if no second squamous cell carcinoma present

Early squamous cell carcinoma of peripheral type
● Defined as tumor 2 cm or less in peripheral lung with no lymph node or distal metastases
● Only rarely identified in practice, since these tumors grow rapidly
● Often have glandular cell characteristics

Basaloid squamous cell carcinoma
● Very aggressive subtype

Spindle cell squamous cell carcinoma
● Also called sarcomatoid carcinoma

Clinical features
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● Most common type of lung cancer in Western countries, although rates are declining due to reduction in tobacco use
● Usually men, closely correlated with smoking history
● Central cases appear to arise from bronchial epithelial dysplasia; peripheral cases usually lack dysplasia
● Symptoms: bronchial obstruction (pneumonitis, atelectasis)
● Associated pleural effusions usually do NOT contain tumor
● May spread to thoracic wall, diaphragm, mediastinum
● Hypercalcemia in a lung tumor not due to bone metastases is usually due to squamous cell carcinoma production of parathyroid hormone-related protein

Gross description
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● Usually central portion of lung affecting larger bronchi but may be peripheral
● Invades peribronchial soft tissue, lung parenchyma and nearby lymph nodes
● May compress pulmonary artery and vein
● Peripheral tumors often have nodular growth with central necrosis and cavitation
● Surrounding lung may exhibit lipid pneumonia, bronchopneumonia, atelectasis
● Calcification is unusual

Gross images
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Central cavitation


Tumor obstructing bronchus


Tumor extending to pleura

Micro description
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● Sheets or islands of large polygonal malignant cells containing keratin (individual cells or keratin pearls) and intercellular bridges
● Adjacent bronchial dysplasia or carcinoma in situ is common
● At advancing tumor border, tumor cells usually destroy alveoli or fill alveolar spaces
● Rarely spreads beneath basement membrane
● May have focal areas of intracytoplasmic mucin
● Rarely oncocytes, foreign body giant cells (reacting to keratin), pallisading granulomas, extensive neutrophilic infiltration, lepidic growth pattern at tumor periphery, clear cell change (glycogen)
● Classify as well, moderately or poorly differentiated based on amount of keratinization present in predominant component
Peripheral tumor types: alveolar space filling (tumor cells fill alveoli but donít destroy elastic septa), expanding type (growth destroys elastic septa) or mixture
Subtypes: basaloid, clear cell (numerous clear tumor cells containing glycogen), small cell (small tumor cells with focal keratinization, distinct nucleoli, sharply outlined tumor nests, less necrosis than small cell neuroendocrine carcinoma), papillary
● Important to examine margins carefully for intraepithelial spread

Micro images
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Well differentiated


Moderately differentiated


Mixed, with keratin pearls and mitotic figures

Virtual slides
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Cavitating tumor


Endobronchial and bronchial tumors


Keratinizing-moderately differentiated


Esophageal metastasis

Cytology description
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● Often positive in sputum

Cytology images
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Sheets of atypical cells with jagged cell borders, basophilic cytoplasm, irregular nuclear contours, nuclear hyperchromasia

Positive stains
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● p63 most common (Arch Pathol Lab Med 2012;136:155, Hum Pathol 2002;33:921); also CK5/6 (87-100%), EMA, thrombomodulin (87-100%)
● Variable CD15, CEA, HPV, mesothelin (16-31%), p53, p40, S100

Negative stains
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● Vimentin (usually), TTF1 (usually), Napsin A

Electron microscopy description
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● Abundant tonofilaments, complex desmosomes, basal lamina

Differential diagnosis
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● Squamous metaplasia with atypia (Hum Pathol 2002;33:1052)

End of Lung tumor > Other carcinoma > Squamous cell carcinoma


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