Non-melanoma skin cancer refers to all types of skin cancer other than melanoma. Although there are several different types of non-melanoma skin cancer, the two most common types are basal cell carcinoma and squamous cell carcinoma.
Basal Cell Carcinoma
Basal cell carcinoma accounts for roughly 80% of all cases of non-melanoma skin cancer. It most commonly develops on sun-exposed skin, with the head (particularly the nose) and neck being the most common sites. The appearance of basal cell carcinoma varies. It often appears as a raised bump with a smooth, pearly or waxy appearance. It may also look like a firm, flat scar. Basal cell carcinoma very rarely metastasizes, but it can cause extensive local damage to the skin and surrounding tissues.
Squamous Cell Carcinoma
Squamous cell carcinoma accounts for roughly 20% of all cases of non-melanoma skin cancer. Squamous cell carcinoma commonly involves the head or neck. The tumor may appear as a red bump or as a rough or scaly area on the skin. Squamous cell carcinoma is more likely than basal cell carcinoma to spread to lymph nodes or distant parts of the body, though this happens infrequently.
Other Types of Non-Melanoma Skin Cancer
Merkel cell carcinoma
Actinic keratoses, also known as solar keratoses because of their link with sun exposure, are a type of precancerous change to the skin. They often appear as rough scaly patches on the skin or as a cracked and peeling area on the lower lip. Actinic keratoses are a warning sign that the skin has been damaged. Without treatment, some actinic keratoses will develop into squamous cell carcinoma.
Diagnosis of Non-Melanoma Skin Cancer
A change to the skin is likely to be the first sign of skin cancer. This may be a sore that doesn’t heal, a new growth, or a change in an old growth.
When non-melanoma skin cancer is suspected, a patient will commonly undergo a complete skin examination. Information about medical history and history of sun exposure will also be collected. If the skin inspection identifies areas that are suspicious for cancer, a physician will conduct a biopsy to remove a sample of the tissue for further examination. A biopsy allows the physician to determine whether cancer is present.
There are several different types of skin biopsies:
Shave biopsy–a razor is used to shave off the abnormal area
Punch biopsy–a circle of tissue is removed from the abnormal area using a special instrument
Excisional biopsy–a scalpel is used to remove the abnormal area
A physician may also examine lymph nodes, since squamous cell carcinoma sometimes spreads to lymph nodes.
Staging of Non-Melanoma Skin Cancer
Stage describes the extent of cancer. Determining cancer stage allows a physician to pick the most appropriate treatment. Skin cancer stage is based on the size of the cancer, the depth of the cancer, and the extent of spread to lymph nodes and beyond.
Stage 0: The cancer involves only the top layer of the skin. This is also called carcinoma in situ.
Stage I: The cancer is 2 cm in diameter or smaller.
Stage II: The cancer is larger than 2 cm in diameter.
Stage III: The cancer has spread below the skin to cartilage, muscle, bone, or nearby lymph nodes, but has not spread to other parts of the body.
Stage IV: The cancer has spread to other parts of the body.
Prognosis of Non-Melanoma Skin Cancer
Because non-melanoma skin cancer very rarely metastasizes, the prognosis is generally very good. There are certain cancer characteristics, however, that are linked with an increased risk of cancer recurrence or metastasis.
Characteristics that are linked with an increased risk of cancer recurrence or metastasis include large tumor size (greater than two centimeters) or greater tumor depth; poorly defined tumor border; tumor location on the head or neck; a suppressed immune system; tumor invasion near a nerve; tumor location at a site of previous radiation therapy; or an aggressive tumor growth pattern. Recurrent tumors also have a higher risk of recurrence or metastasis. For patients with squamous cell carcinoma, high-risk tumor locations also include the genitals and sites of chronic inflammation or scarring.
During the first five years after a diagnosis of non-melanoma skin cancer, between 30% and 50% of patients will develop another non-melanoma skin cancer. Individuals who have had non-melanoma skin cancer are also at increased risk of developing melanoma.
Surgery is the mainstay of treatment for non-melanoma skin cancers. There are several different types of surgery, and the choice of which to use will depend in part on the location and characteristics of the cancer. Other treatment options include radiation therapy, photodynamic therapy, and topical therapy. For more detailed information about treatment of non-melanoma skin cancer, go to Treatment of Non-melanoma Skin Cancer
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 National Comprehensive Cancer Network. Basal Cell and Squamous Cell Skin Cancers. Clinical Practice Guidelines in Oncology – v.2.2005. © National Comprehensive Cancer Network, Inc. 2001, 2002, 2003, 2004, 2005. NCCN and NATIONAL COMPREHENSIVE CANCER NETWORK are registered trademarks of National Comprehensive Cancer Network, Inc.
 Rosenberg CA, Khandekar J, Greenland P et al. Cutaneous Melanoma in Postmenopausal Women After Nonmelanoma Skin Carcinoma: The Women’s Health Initiative Observational Study. Cancer. 2006;106:654-63.