Squamous cell carcinoma of the lung

This is the most common form of lung tumour accounting for approximately 40% of cases. It is more common in males and is the lung tumour most closely associated with cigarette smoking.

• typically centrally located and often larger than 4 cm in diameter
  • most affect the large, segmental, more central bronchi
  • tumour may be silent initially, but causes progressive narrowing of the bronchi until obstruction ensues, leading to distal collapse, bronchiectasis and lung abscesses.
• cavitation is seen in up to 82%
  • grey / white in colour, and may extend into the adjacent lung, pleura and hilar nodes
• due to their central location segmental or lobar collapse is common.

Microscopic features include keratinisation and intercellular bridge formation - 'prickles'. Squamous dysplasia, metaplasia, or carcinoma in situ may be observed in the vicinity of the tumour.

Local growth is rapid.Metastasis occurs via lymphatic and haematogenous routes, but tends to be later than for other types of carcinoma.

• prognosis is better for squamous carcinoma than for other lung malignancies. Although in part this is because squamous carcinoma is typically localised to the chest at presentation most investigators have found a better stage-for-stage prognosis in squamous cell carcinoma, than adenocarcinoma or large cell carcinoma (1)

Spindle cell squamous carcinoma is a variant which may be misdiagnosed as sarcoma. However, immunohistochemical staining and electron microscopy clearly differentiate the two.

Reference:

• (1) Beadsmoore CJ, Screaton NJ. Classification, staging and prognosis of lung cancer. European Journal of Radiology 2003; 45 (1): 8-17.