Squamous-cell carcinoma of the lung

Squamous-cell carcinoma (SCC) of the lung is a type of non-small-cell lung carcinoma and is more common in men than in women. It is closely correlated with a history of tobacco smoking, more so than most other types of lung cancer. According to the Nurses' Health Study, the relative risk of SCC is approximately 5.5, both among those with a previous duration of smoking of 1 to 20 years, and those with 20 to 30 years, compared to never-smokers.[1] The relative risk increases to approximately 16 with a previous smoking duration of 30 to 40 years, and approximately 22 with more than 40 years.[1]

Description

It most often arises centrally in larger bronchi, and while it often metastasizes to locoregional lymph nodes (particularly the hilar nodes) early in its course, it generally disseminates outside the thorax somewhat later than other major types of lung cancer. Large tumors may undergo central necrosis, resulting in cavitation. A squamous-cell carcinoma is often preceded for years by squamous-cell metaplasia or dysplasia in the respiratory epithelium of the bronchi, which later transforms to carcinoma in situ.

In carcinoma in situ, atypical cells may be identified by cytologic smear test of sputum, bronchoalveolar lavage or samples from endobronchial brushings. However, squamous-cell carcinoma in situ is asymptomatic and undetectable on X-ray radiographs.

Eventually, it becomes symptomatic, usually when the tumor mass begins to obstruct the lumen of a major bronchus, often producing distal atelectasis and infection. Simultaneously, the lesion invades into the surrounding pulmonary substance. On histopathology, these tumors range from well differentiated, showing keratin pearls and cell junctions, to anaplastic, with only minimal residual squamous-cell features.[2]

Variants

Currently, four variants (papillary, small-cell, clear-cell, and basaloid) of squamous-cell carcinoma of the lung are recognized. Of these variants, there is some evidence that the basaloid[3] and poorly differentiated small-cell variants [4] may have worse prognoses than "conventional" squamous-cell carcinomas. The papillary variant occurs more frequently as a primarily superficial, endobronchial lesion, with a modestly better prognosis[5] Very little data is currently available on the clear-cell variant of squamous-cell carcinoma, and no consensus has been reached on the prognostic implications of clear-cell changes in lung cancer.[6][7]

RNA expression profiles

Recently, four mRNA expression subtypes (primitive, basal, secretory, and classical) were identified and validated within squamous-cell carcinoma. The primitive subtype correlates with worse patient survival. These subtypes, defined by intrinsic expression differences, provide a possible foundation for improved patient prognosis and research into individualized therapies.[8]

References

  1. 1 2 Kenfield, S. A.; Wei, E. K.; Stampfer, M. J.; Rosner, B. A.; Colditz, G. A. (2008). "Comparison of aspects of smoking among the four histological types of lung cancer". Tobacco Control 17 (3): 198–204. doi:10.1136/tc.2007.022582. PMC 3044470. PMID 18390646.
  2. ↑ Entire section, if not else specified, is taken from Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson. "Ch. 13, box on morphology of squamous cell carcinoma". Robbins Basic Pathology (8th ed.). Philadelphia: Saunders. ISBN 1-4160-2973-7.
  3. ↑ Wang, LC; Wang, L; Kwauk, S; Woo, JA; Wu, LQ; Zhu, H; Zhan, LZ; Sun, NL; Zhang, L (2011). "Analysis on the clinical features of 22 basaloid squamous-cell carcinoma of the lung". Journal of Cardiothoracic Surgery 6: 10. doi:10.1186/1749-8090-6-10. PMC 3037842. PMID 21269455.
  4. ↑ Travis, William D; Brambilla, Elisabeth; Muller-Hermelink, H Konrad; et al., eds. (2004). Pathology and Genetics of Tumours of the Lung, Pleura, Thymus and Heart (PDF). World Health Organization Classification of Tumours. Lyon: IARC Press. ISBN 92-832-2418-3. Retrieved 27 March 2010.
  5. ↑ Dulmet-Brender E, Jaubert F, Huchon G (April 1986). "Exophytic endobronchial epidermoid carcinoma". Cancer 57 (7): 1358–64. doi:10.1002/1097-0142(19860401)57:7<1358::AID-CNCR2820570719>3.0.CO;2-B. PMID 3948117.
  6. ↑ Kitada M, Ozawa K, Sato K, Hayashi S, Miyokawa N, Sasajima T (February 2010). "Clear cell carcinoma of the lung". Gen Thorac Cardiovasc Surg 58 (2): 87–90. doi:10.1007/s11748-009-0471-8. PMID 20155345., which are usually due to increased levels of intracellular glycogen (or, rarely, biotin).
  7. ↑ Garzon, JC; Lai, FM; Mok, TS; Manlulu, AV; Ng, CS; Lee, TW; Yim, AP (2005). "Clear cell carcinoma of the lung revisited". The Journal of thoracic and cardiovascular surgery 130 (4): 1198–9. doi:10.1016/j.jtcvs.2005.04.030. PMID 16214540.
  8. ↑ Wilkerson, MD; Yin, X; Hoadley, KA; Liu, Y; Hayward, MC; Cabanski, CR; Muldrew, K; Miller, CR; Randell, SH; Socinski, M. A.; Parsons, A. M.; Funkhouser, W. K.; Lee, C. B.; Roberts, P. J.; Thorne, L.; Bernard, P. S.; Perou, C. M.; Hayes, D. N. (2010). "Lung squamous cell carcinoma mRNA expression subtypes are reproducible, clinically important, and correspond to normal cell types". Clinical cancer research : an official journal of the American Association for Cancer Research 16 (19): 4864–75. doi:10.1158/1078-0432.CCR-10-0199. PMC 2953768. PMID 20643781.
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