Squamous Cell Carcinoma Risks and Diagnosis

Understanding the Second Most Common Type of Skin Cancer

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

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 1940s
  • 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.

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Squamous cell carcinoma
DermNet / CC BY-NC-ND 


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.


Treatment options for this skin cancer depend on information gleaned from the biopsy.

Electrodesiccation and curettage - This procedure involves destroying the skin cancer with an electrocautery device then scraping the area with a curet. Many times the diseased tissue can be differentiated from the normal tissue by the texture felt while scraping. This process is repeated several times to ensure complete removal of the skin cancer. This procedure is useful for small tumors 1 cm or less in diameter on the neck, trunk, arms, or legs. However, it tends to leave a scar.

Simple excision - This procedure involves surgical excision of the skin cancer including a margin of normal skin. For tumors of 2 cm or less, a margin of 4 mm is sufficient; for tumors >2 cm, the best margin is 6 mm. The advantage of this treatment is that it is quick and inexpensive. However, the difference between normal and cancerous tissue must be judged with the naked eye.

Mohs' micrographic surgery - This procedure is must be performed by an experienced Mohs' surgeon. It involves excision of the skin cancer and immediate examination of the tissue under the microscope to determine margins. If any residual skin cancer is left, it can be mapped out and excised immediately. The process of excision and examination of margins may have to be repeated several times. The advantage of this technique is that it is usually definitive and has been reported to have a lower recurrence rate than other treatment options. The disadvantage is the time and expense involved.

Radiation therapy - This procedure involves a course of radiation therapy to the tumor area. At this time, however, there is insufficient evidence that radiation after surgery improves the recurrence rate of squamous cell carcinoma. It can also have the long-term effects of scarring, ulceration, and thinning of the skin.

Chemotherapy - The type of chemotherapy used is 13-cis-Retinoic acid and interferon-2A. Chemotherapy is used for advanced stages of squamous cell carcinoma.

Cryotherapy - This procedure involves destroying the tissue by freezing it with liquid nitrogen. This may be effective for small, well-defined superficial skin cancers. It is also used effectively for the treatment of actinic keratosis, a premalignant condition. This procedure is inexpensive and time-efficient but can only be used in a small number of cases.


Avoid UVB radiation from sun exposure - Avoid the midday sun, use protective clothing, and use sunscreen with an SPF of at least 15. This is especially important for children.

Avoid tobacco products - This includes cigars, cigarettes, chewing tobacco, and snuff. Since these products increase the risk of squamous cell carcinoma on lip and mouth, their use should be reduced or cut out altogether.

Avoid polycyclic hydrocarbons - Jobs that require contact with these compounds are highly regulated. Use protective gear at all times while working with these compounds.

Have suspicious lesions checked out - If you have a question, get it checked out. Treating premalignant lesions prevents their transformation to potentially metastatic skin cancer.

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