Squamous cell carcinoma of the lung 1

Squamous cell carcinoma of the lungSquamous cell carcinoma (SCC) of the lung is more common in men than in women. It is closely correlated with ahistory 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 20years, and those with 20 to 30 years, compared to never-smokers. The relative risk increases to approximately 16with a previous smoking duration of 30 to 40 years, and approximately 22 with more than 40 years.

DescriptionIt 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 thanother major types of lung cancer. Large tumors may undergo central necrosis, resulting in cavitation. A squamouscell carcinoma is often preceded for years by squamous cell metaplasia or dysplasia in the respiratory epithelium ofthe 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 orsamples from endobronchial brushings. However, squamous-cell carcinoma in situ is asymptomatic and undetectableon 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 pulmonarysubstance. On histopathology, these tumors range from well differentiated, showing keratin pearls and cell junctions,to anaplastic, with only minimal residual squamous cell features.[1]

VariantsCurrently, four variants (papillary, small cell, clear cell, and basaloid) of squamous cell carcinoma of the lung arerecognized. Of these variants, there is some evidence that the basaloid and poorly differentiated small-cell variantsmay have worse prognoses than "conventional" squamous cell carcinomas. The papillary variant occurs morefrequently as a primarily superficial, endobronchial lesion, with a modestly better prognosis Very little data iscurrently available on the clear cell variant of squamous cell carcinoma, and no consensus has been reached on theprognostic implications of clear cell changes in lung cancer.[2]

RNA expression profilesRecently, four mRNA expression subtypes (primitive, basal, secretory, and classical) were identified and validatedwithin 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 andresearch into individualized therapies.

References[1][1] Entire section, if not else specified, is taken from[2][2] , which are usually due to increased levels of intracellular glycogen (or, rarely, biotin).

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Article Sources and ContributorsSquamous cell carcinoma of the lung  Source: http://en.wikipedia.org/w/index.php?oldid=595865580  Contributors: Patho

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