Non Small Cell Lung Cancer Histology: Histological Classification of Lung Cancer

Posted on July 17, 2009 by mkr in Respiratory & Lung Diseases

Lung Cancer Histology

Histological classification of non-small cell lung cancer, which is the most common in bronchogenic carcinoma (70 to 75%), can be made in to -

  1. Squamous cell (epidermoid) carcinoma (25-30%).
  2. i. Adenocarcinomas, including  ii. Bronchioloalveolar carcinoma (30-35%).
  3. Large cell carcinoma (10-15%).

Squamous cell carcinomas

  • They are most common in men than in women and tend to arise centrally in major bronchi and eventually spread to local hilar nodes, but they disseminate outside the thorax later than the other histological types.
  • Squamous cell carcinomas are often preceded for years by atypical metaplasia or dysplasia in the bronchial epithelium, which then transforms to carcinoma in situ, a phase that may last for several years.
  • A small area (1 to 2 cm in diameter) of thickened, irregularly nodular mucosa gradually develops. By this time, a typical cells may be identified in the cytological smears of sputum or in bronchial lavage fluid although the lesion may be undetectable on the radiographs.
  • Eventually this reaches a symptomatic stage, when a well defined tumor mass begins to obstruct the lumen of a major bronchus, often producing distal atelectasis and infection.

Histological Classification of  Squamous cell carcinomas

  • These tumors range from well differentiated squamous cell neoplasms showing keratin pearls and inter-cellular bridges.
  • Squamous cell carcinomas have slightly better prognosis than other histological types because they tend to develop into large, bulky, centrally obstructing symptomatic masses before they metastasize and are, therefore, more often surgically re-sectable.

Adenocarcinomas

  • They are almost equally common in males and females and the association with cigarette smoking is weaker than for squamous cell carcinoma.
  • They may occur as central lesions like the squamous cell variant but are usually more peripherally located, many arising in relation to peripheral lung scars. In general, these tumors grow slowly and form smaller masses than do the other sub-types, but they tend to metastasize widely at an early stage.

Histological Classification of Adenocarcinomas

  • The neoplastic cells are generally cuboidal to columnar, frequently secrete mucin and typically form tubular, acinar or papillary structures.

Bronchioloalveolar carcinoma

  • It is a special category of adenocarcinoma which occurs as two variants.
  • Less than half of bronchioloalveolar carcinomaare multifocal mucinous masses that sometimes are discrete but at other times coalescent.
  • Most often they are confined to single lobe, but they sometimes involve multiple lobes and may even be bilateral.

Histological Classification of  Bronchioloalveolar carcinoma

  • These masses consist of tall columnar cells, regularly arrayed along preserved alveolar septa, having abundant intra and extra-cellular mucin and basally located small nuclei. The cytologic appearance is deceptively benign and mitosis is rare.
  • The other variant is a single, localized gray-white nodule that may be up to 10cm in diameter and is most often situated near the periphery in the upper lobe.
  • Bronchioloalveolar carcinoma has a better prognosis than other bronchogenic carcinoma, the multifocal variant has a 20 to 25% five year survival rate and the localized single mass has a 50 to 70% five year survival rate.

Read about: Non small cell lung cancer life expectancy

Large cell carcinomas

  • It constitutes the group of neoplasms that lack cytologic differentiation and probably represent squamous cell or glandular neoplasms that are too undifferentiated to permit categorization.
  • The cells are usually anaplastic and have large vesicular nuclei. These neoplasms are generally bulky and are more often peripheral than central.
  • They have a poor prognosis because of their tendency to spread to distant sites early in their course. More than half involve the central nervous system at the time of diagnosis and the five year survival rate is 2 to 3%.

Leave a Reply

Your email address will not be published.