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Cellular Classification of Skin Cancer


    Squamous Cell Carcinoma

    SCCs also tend to occur on sun-exposed portions of the skin, such as the ears, lower lip, and dorsa of the hands. However, SCCs that arise in areas of non–sun-exposed skin or that originate de novo on areas of sun-exposed skin are prognostically worse because they have a greater tendency to metastasize than those that occur on sun-exposed skin that develop from actinic keratosis. People with chronic sun damage, sites of prior burns, arsenic exposure, chronic cutaneous inflammation as seen in longstanding skin ulcers, and sites of previous x-ray therapy are predisposed to the development of SCC.[4]

    SCCs are composed of keratinizing cells. These tumors are more aggressive than BCCs and have a range of growth, invasive, and metastatic potential. Prognosis is associated with the degree of differentiation, and tumor grade is reported as part of the staging system.[2] A four-grade system (G1–G4) is most common, but two- and three-grade systems may also be used. Mutations in the PTCH1 tumor suppressor gene have been reported in SCCs removed from patients with a prior history of multiple BCCs.[5]

    SCC in situ (also called Bowen disease) is a noninvasive lesion. It may be difficult to distinguish it pathologically from a benign inflammatory process.[1] The risk of development into invasive SCC is low, reportedly in the 3% to 4% range.[6]

    Actinic Keratosis

    Actinic keratoses are potential precursors of SCC, but the rate of progression is extremely low, and the vast majority do not become SCCs. These typically red, scaly patches usually arise on areas of chronically sun-exposed skin and are likely to be found on the face and dorsal aspects of the hand.


    1. Reszko A, Aasi SZ, Wilson LD, et al.: Cancer of the skin. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2011, pp 1610-33.
    2. Cutaneous squamous cell carcinoma and other cutaneous carcinomas. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 301–14.
    3. Dubin N, Kopf AW: Multivariate risk score for recurrence of cutaneous basal cell carcinomas. Arch Dermatol 119 (5): 373-7, 1983.
    4. Wagner RF, Casciato DA: Skin cancers. In: Casciato DA, Lowitz BB, eds.: Manual of Clinical Oncology. 4th ed. Philadelphia, Pa: Lippincott, Williams, and Wilkins, 2000, pp 336-373.
    5. Ping XL, Ratner D, Zhang H, et al.: PTCH mutations in squamous cell carcinoma of the skin. J Invest Dermatol 116 (4): 614-6, 2001.
    6. Kao GF: Carcinoma arising in Bowen's disease. Arch Dermatol 122 (10): 1124-6, 1986.

    This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http:// cancer .gov or call 1-800-4-CANCER.

    WebMD Public Information from the National Cancer Institute

    Last Updated: February 25, 2014
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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