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Squamous Cell Carcinoma

Basic Information About Squamous Cell Carcinoma

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Updated July 23, 2008

Squamous cell carcinoma (SCC) is the second most common type of skin cancer. It occurs more often in men than in women at a 2:1 ratio. The incidence of squamous cell carcinoma among Caucasians in the US is .1-.15% per year. The incidence increases with age and the peak incidence of this skin cancer is at 66 years. The incidence also increases with decreasing latitudes such as the southern US and Australia.

What is Squamous Cell Carcinoma?
Squamous cell carcinoma arises in the outer layer of the skin, the epidermis, causing mutations in cells called keratinocytes. UVB radiation is important for the induction of this skin cancer damaging DNA and its repair system, also causing mutations in tumor-suppressing genes. These mutated cells spread superficially and cause the appearance of the skin to change. When the mutated cells penetrate the dermis, the risk of metastasis increases.

Risk Factors for Squamous Cell Carcinoma
Some common squamous cell carcinoma risk factors include:

  • Chronic sun exposure mainly to UVB radiation but also UVA
  • A premalignant condition called actinic keratosis or solar keratosis
  • A suppressed immune system
  • HIV disease
  • Ionizing radiation used for acne in the 1940's
  • Fair skin
  • Tobacco use

Some rare squamous cell carcinoma risk factors include:

  • Exposure to arsenic
  • Exposure to cyclic aromatic hydrocarbons in tar, soot, or shale
  • Scarred or previously damaged skin, especially radiation damage
  • Infection with human papillomavirus types 6, 11, 16, and 18
  • A rare genetic disease called xeroderma pigmentosa

Appearance of Squamous Cell Carcinoma
The skin change caused by squamous cell carcinoma most often looks like a scab. There may be a thick, adherent scale on a red, inflamed base. Normally a scab will significantly heal within 2 weeks. However, squamous cell carcinoma does not heal and may intermittently bleed. As it spreads into the dermis, this skin cancer can appear like an ulcer with hard, raised edges. The most common areas squamous cell carcinoma is found are in sun-exposed areas such as the back of the hand, scalp, lip, and upper portion of the ear.

Pictures of Squamous Cell Carcinoma
The following pictures show various squamous cell carcinoma lesions:

Diagnosis of Squamous Cell Carcinoma
The only way to diagnose squamous cell carcinoma is to biopsy suspicious looking lesions. The preferred type of biopsy is called a shave biopsy in which the lesion is shaved off with a flexible razor. Depending on the extent of the lesion, another biopsy option is to excise the lesion. Useful information such as whether the complete tumor was removed and tumor depth can only be obtained by biopsy.

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