Font Size
A
A
A
2
...

Non-Small Cell Lung Cancer Treatment (Professional) (cont.)

Cellular Classification of NSCLC

Malignant non-small cell epithelial tumors of the lung are classified by the World Health Organization (WHO)/International Association for the Study of Lung Cancer (IASLC). There are three main subtypes of NSCLC, including the following:

  • Squamous cell carcinoma (25% of lung cancers).
  • Adenocarcinoma (40% of lung cancers).
  • Large cell carcinoma (10% of lung cancers).

There are numerous additional subtypes of decreasing frequency.[1]

WHO/IASLC Histologic Classification of NSCLC

  1. Squamous cell carcinoma.
    • Papillary.
    • Clear cell.
    • Small cell.
    • Basaloid.
  2. Adenocarcinoma.
    • Acinar.
    • Papillary.
    • Bronchioloalveolar carcinoma.
      • Nonmucinous.
      • Mucinous.
      • Mixed mucinous and nonmucinous or indeterminate cell type.
    • Solid adenocarcinoma with mucin.
    • Adenocarcinoma with mixed subtypes.
    • Variants.
      • Well-differentiated fetal adenocarcinoma.
      • Mucinous (colloid) adenocarcinoma.
      • Mucinous cystadenocarcinoma.
      • Signet ring adenocarcinoma.
      • Clear cell adenocarcinoma.
  3. Large cell carcinoma.
    • Variants.
      • Large cell neuroendocrine carcinoma (LCNEC).
      • Combined LCNEC.
      • Basaloid carcinoma.
      • Lymphoepithelioma-like carcinoma.
      • Clear cell carcinoma.
      • Large cell carcinoma with rhabdoid phenotype.
  4. Adenosquamous carcinoma.
  5. Carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements.
    • Carcinomas with spindle and/or giant cells.
    • Spindle cell carcinoma.
    • Giant cell carcinoma.
    • Carcinosarcoma.
    • Pulmonary blastoma.
  6. Carcinoid tumor.
    • Typical carcinoid.
    • Atypical carcinoid.
  7. Carcinomas of salivary gland type.
    • Mucoepidermoid carcinoma.
    • Adenoid cystic carcinoma.
    • Others.
  8. Unclassified carcinoma.

Squamous cell carcinoma

Most squamous cell carcinomas of the lung are located centrally, in the larger bronchi of the lung. Squamous cell carcinomas are linked more strongly with smoking than other forms of NSCLC. The incidence of squamous cell carcinoma of the lung has been decreasing in recent years.

Adenocarcinoma

Adenocarcinoma is now the most common histologic subtype in many countries, and subclassification of adenocarcinoma is important. One of the biggest problems with lung adenocarcinomas is the frequent histologic heterogeneity. In fact, mixtures of adenocarcinoma histologic subtypes are more common than tumors consisting purely of a single pattern of acinar, papillary, bronchioloalveolar, and solid adenocarcinoma with mucin formation.

Criteria for the diagnosis of bronchioloalveolar carcinoma have varied widely in the past. The current WHO/IASLC definition is much more restrictive than that previously used by many pathologists because it is limited to only noninvasive tumors.

If stromal, vascular, or pleural invasion are identified in an adenocarcinoma that has an extensive bronchioloalveolar carcinoma component, the classification would be an adenocarcinoma of mixed subtype with predominant bronchioloalveolar pattern and a focal acinar, solid, or papillary pattern, depending on which pattern is seen in the invasive component.

The following variants of adenocarcinoma are recognized in the WHO/IASLC classification:

  • Well-differentiated fetal adenocarcinoma.
  • Mucinous (colloid) adenocarcinoma.
  • Mucinous cystadenocarcinoma.
  • Signet ring adenocarcinoma.
  • Clear cell adenocarcinoma.

Large cell carcinoma

In addition to the general category of large cell carcinoma, several uncommon variants are recognized in the WHO/IASLC classification, including the following:

  • LCNEC.
  • Basaloid carcinoma.
  • Lymphoepithelioma-like carcinoma.
  • Clear cell carcinoma.
  • Large cell carcinoma with rhabdoid phenotype.

Basaloid carcinoma is also recognized as a variant of squamous cell carcinoma, and rarely, adenocarcinomas may have a basaloid pattern; however, in tumors without either of these features, they are regarded as a variant of large cell carcinoma.

Neuroendocrine tumors

LCNEC is recognized as a histologically high-grade non-small cell carcinoma. It has a very poor prognosis similar to that of small cell lung cancer (SCLC). Atypical carcinoid is recognized as an intermediate-grade neuroendocrine tumor with a prognosis that falls between typical carcinoid and high-grade SCLC and LCNEC.

Neuroendocrine differentiation can be demonstrated by immunohistochemistry or electron microscopy in 10% to 20% of common NSCLCs that do not have any neuroendocrine morphology. These tumors are not formally recognized within the WHO/IASLC classification scheme because the clinical and therapeutic significance of neuroendocrine differentiation in NSCLC is not firmly established. These tumors are referred to collectively as NSCLC with neuroendocrine differentiation.

Carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements

This is a group of rare tumors. Spindle cell carcinomas and giant cell carcinomas comprise only 0.4% of all lung malignancies, and carcinosarcomas comprise only 0.1% of all lung malignancies. In addition, this group of tumors reflects a continuum in histologic heterogeneity as well as epithelial and mesenchymal differentiation. On the basis of clinical and molecular data, biphasic pulmonary blastoma is regarded as part of the spectrum of carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements.

References:

  1. Travis WD, Colby TV, Corrin B, et al.: Histological typing of lung and pleural tumours. 3rd ed. Berlin: Springer-Verlag, 1999.
2
...
eMedicineHealth Public Information from the National Cancer Institute

This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http://cancer.gov or call 1-800-4-CANCER

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Some material in CancerNet™ is from copyrighted publications of the respective copyright claimants. Users of CancerNet™ are referred to the publication data appearing in the bibliographic citations, as well as to the copyright notices appearing in the original publication, all of which are hereby incorporated by reference.





Medical Dictionary