Lung tumor
Other carcinoma

Editorial Board Member: Andrey Bychkov, M.D., Ph.D.
Roseann Wu, M.D., M.P.H.

Topic Completed: 1 March 2017

Minor changes: 4 July 2020

Revised: 31 January 2019, last major update March 2017

Copyright: (c) 2003-2018,, Inc.

PubMed Search: adenosquamous carcinoma [title] lung

Roseann Wu, M.D., M.P.H.
Page views in 2019: 6,359
Page views in 2020 to date: 3,538
Cite this page: Wu R. Adenosquamous. website. Accessed August 7th, 2020.
Definition / general
  • Substantial amounts of malignant squamous and glandular differentiation (at least 10% of each component within tumor)
  • 90% peripheral, often associated with scars, with clinical / imaging features similar to adenocarcinoma
  • Poorer prognosis than either component alone
Essential features
  • WHO classification as non-small cell lung carcinoma with at least 10% components of both adenocarcinoma and squamous cell carcinoma by histomorphology
  • Diagnosis made on resection specimens, although it may be suspected on biopsy or cytology
  • May harbor targetable molecular alterations seen in adenocarcinomas
  • By WHO classification, adenosquamous carcinoma contains at least 10% each of malignant squamous and glandular components
  • Differentiate from adenocarcinoma with squamoid features / squamous metaplasia as well as squamous cell carcinoma with pseudoglandular features
ICD coding
  • Use code specific for location of tumor
  • C34.90 Malignant neoplasm of unspecified part of unspecified bronchus or lung
  • Tends to arise peripherally but may be central
  • More aggressive than "pure" carcinomas when matched for stage
  • Association with smoking, similar to other lung cancers
Clinical features
  • Similar to lung adenocarcinoma
  • Diagnosis made on resection specimens, though can be suggested in biopsy or cytology as follows:
    • Non-small cell carcinoma, see note
    • Note: Glandular and squamous components are present; the findings could represent adenosquamous carcinoma
Radiology description
Prognostic factors
  • Worse than "pure" adenocarcinoma or squamous cell carcinoma; associated with larger size, visceral pleural invasion, lymphatic invasion, ipsilateral second nodules (Ann Thorac Surg 2013;95:1189)
  • EGFR mutated adenosquamous carcinomas appear to have better prognosis (Pathol Int 2013;63:77)
Case reports
Gross description
  • Similar to adenocarcinoma but may show more aggressive features, i.e. larger size, pleural invasion
Gross images

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Adenosquamous carcinoma of lung

Microscopic (histologic) description
  • Malignant cells with squamous or glandular differentiation with variable degree of admixture
  • Squamous component may show keratin, intercellular bridges, squamous pearls
  • Glandular components may show lumens with mucin; may have papillary, lepidic, acinar or tubular patterns
  • Metastasis in lymph node tend to be same histologic type as the major component (Cancer 1991;67:649) but not necessarily
Microscopic (histologic) images

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Contributed by Roseann Wu, M.D., M.P.H.

Images hosted on Flickr:

Various images

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Adenosquamous carcinoma

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Transbronchial lung biopsy with adenocarcinoma and squamous cell carcinoma

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Adenocarcinoma forming mucous membranes and parts of the squamous epithelial carcinoma

Virtual slides

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Rosai collection: Adenosquamous carcinoma in lung

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LeedsUni collection: F 63 yo, right lobectomy

Cytology description
  • Variable depending on squamous or glandular components and degree of differentiation
Cytology images

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Adenosquamous carcinoma

Positive stains
Negative stains
  • Neuroendocrine markers
Molecular / cytogenetics description
Molecular / cytogenetics images

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With KRas and EGFR mutations


Differential diagnosis
Board review style question #1
Pulmonary adenosquamous carcinoma:

  1. Has a better prognosis than pure adenocarcinoma or squamous cell carcinoma.
  2. Always shows both components in metastases.
  3. Requires immunohistochemistry for diagnosis.
  4. May harbor EGFR or Kras mutations.
  5. Shows a benign squamous component.
Board review answer #1
D. May harbor EGFR or Kras mutations.

It is important to recognize pulmonary adenosquamous carcinoma, as these tumors may harbor targetable mutations seen in adenocarcinomas, such as EGFR or Kras. Pulmonary adenosquamous carcinoma has a worse prognosis than either adenocarcinoma or squamous carcinoma. Only one of the two components may be seen in metastatic sites. The diagnosis is made with at least 10% of each component by histology, not immunohistochemistry. Both the adenocarcinoma and squamous cell carcinoma components are malignant.
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