Lung
Other carcinomas
Adenosquamous
Author: Roseann I. Wu, M.D., M.P.H.
Editorial Board Member: Andrey Bychkov, M.D., Ph.D.
Last author update: 1 March 2017
Last staff update: 26 December 2023 (update in progress)
Copyright: 2003-2025, PathologyOutlines.com, Inc.
PubMed Search: adenosquamous carcinoma [title] lung
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Radiology description | Prognostic factors | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Virtual slides | Cytology description | Cytology images | Positive stains | Negative stains | Molecular / cytogenetics description | Molecular / cytogenetics images | Videos | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Wu R. Adenosquamous. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungtumoradenosquamous.html. Accessed January 20th, 2025.
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
Terminology
- 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
Epidemiology
- Uncommon, 1 - 5% of lung cancers
- Similar age and sex distribution to other lung cancers (Am J Clin Oncol 1992;15:356)
Sites
- Tends to arise peripherally but may be central
Pathophysiology
- More aggressive than "pure" carcinomas when matched for stage
Etiology
- Association with smoking, similar to other lung cancers
Clinical features
- Similar to lung adenocarcinoma
Diagnosis
- 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
- Peripheral tumor, averages 3 - 4 cm
- Lobulated to spiculated, ill defined borders (Clin Nucl Med 2014;39:107)
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
- 57 year old man with metastasis of lung adenosquamous carcinoma to meningioma (Int J Clin Exp Pathol 2013;6:2625)
- 58 year old man with ALK rearranged adenosquamous cancer masquerading as pure squamous cell carcinoma (J Thorac Oncol 2012;7:768)
- 60 year old man with cutaneous leukocytoclastic vasculitis presenting as the first symptom of adenosquamous carcinoma of the lung (J Korean Rheum Assoc 2010;17:272)
- 60 year old woman with EGFR mutated adenosquamous carcinoma with micropapillary pattern (Respirol Case Rep 2016;4:e00179)
- 65 year old man who received chemoradiation therapy for limited stage small cell lung carcinoma (SCLC) (Haigan 2011;3:182)
- 66 year old woman with adenosquamous cell lung cancer successfully treated with gefitinib (Mol Clin Oncol 2014;2:282)
- 68 year old man presenting with a solitary pulmonary nodule at the right lower lobe (Korean J of Path 2004;15:101)
- 69 year old woman with EGFR mutated adenosquamous lung carcinoma (Soonchunhyang Med Sci 2013;19:123)
- 71 year old man with cytology consistent with adenosquamous carcinoma (Diagn Cytopathol 2012;40:830)
- 76 year old man with lung cancer and multiple metastases (CEN Case Rep 2013;2:158)
Treatment
- Surgical resection
- EGFR tyrosine kinase inhibitors may be considered for those harboring this mutation (J Cancer Res Clin Oncol 2016;142:1325)
Gross description
- Similar to adenocarcinoma but may show more aggressive features, i.e. larger size, pleural invasion
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
Contributed by Roseann Wu, M.D., M.P.H. and Yale Rosen, M.D.
Adenosquamous carcinoma
Images hosted on other servers:
Transbronchial lung biopsy with adenocarcinoma and squamous cell carcinoma
Adenocarcinoma forming mucous membranes and parts of the squamous epithelial carcinoma
Virtual slides
Images hosted on other servers:
Rosai collection: adenosquamous carcinoma in lung
Leeds University collection: 63 year old female, right lobectomy
Cytology description
- Variable depending on squamous or glandular components and degree of differentiation
Cytology images
Images hosted on other servers:
Adenosquamous carcinoma
Positive stains
Negative stains
- Neuroendocrine markers
Molecular / cytogenetics description
- EGFR and KRAS mutations detected in some cases; mutation profile shared by both glandular and squamous components (Am J Clin Pathol 2011;135:783; Histopathology 2015;66:939)
- Tumors with even minor adenocarcinoma component can still show KRAS and EGFR mutations (Chest 2014;145:473)
Molecular / cytogenetics images
Images hosted on other servers:
With KRAS and EGFR mutations
Videos
Differential diagnosis
- Adenocarcinoma with "squamoid" features or foci of benign squamous metaplasia
- Collision tumor
- High grade mucoepidermoid carcinoma: central airways
- Squamous cell carcinoma with pseudoglandular features or entrapped epithelium
Additional references
Board review style question #1
Which of the following is true about pulmonary adenosquamous carcinoma?
- Has a better prognosis than pure adenocarcinoma or squamous cell carcinoma
- Always shows both components in metastases
- Requires immunohistochemistry for diagnosis
- May harbor EGFR or Kras mutations
- Shows a benign squamous component
Board review style 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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