Skin cancer is one of the most common types of cancer in the U.S. with nearly 1,000,000 new cases each year. Nearly every Caucasian over the age of 65 will have at least one case of skin cancer. Fortunately, the two most common types, basal cell carcinoma and squamous cell carcinoma, are easily treated and if caught early can be completely cured. For all types of skin cancer risk factors include: 1) exposure to UV light from the sun and/or tanning beds; 2) having a fair complexion (recall that melanin absorbs UV light and protects us from its damaging effects) and; 3) occupational hazards such as exposure to coal tar, creosote and arsenic compounds, to name a few.

Basal Cell Carcinoma

Basal cell carcinoma is the most common type of skin cancer. It develops in cells of the hair follicles, sebaceous glands or interfollicular basal cells. The most common sites for this type of cancer are the face and neck. It grows very slowly and rarely metastasizes (spread of cancer when cells from the tumor break off and travel through the blood or lymph to other parts of the body where they form new tumors). It starts as a pearly or ivory colored growth, which later develops a depressed center and a ridged border. As it continues to grow it may develop an ulcer in the center and take on a crusty appearance. Because of its slow growth it is relatively easy to treat and surgical removal results in complete cure in 99% of cases. Look at examples of basal cell carcinomas.

Author: Michael Kahn, Tufts University OpenCourseware. Licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. Link: http://ocw.tufts.edu/Content/51/lecturenotes/551485/551637

Squamous Cell Carcinoma

Squamous cell carcinoma typically appears in the squamous cells of the epidermis (although it generally originates from the cells of the stratum spinosum). The primary lesion is usually confined to the epidermis but may extend into the upper layers of the dermis. It has a greater tendency to metastasize than basal cell carcinoma, hence it is important to identify and treat it sooner. These tumors arise from preexisting lesions such as sun damaged skin (actinic dermatitis), scars or chronic skin ulcers, to name a few. Ninety percent of squamous cell carcinomas are found on the head, neck and hands, the other 10% can occur anywhere on the body. These tumors are relatively firm, as they grow they increase in both height and diameter and the surface may be granular and bleed easily. Treatment includes surgical removal or treatment with radiation. If detected and treated early the chances of complete recovery are good. Look at the example of squamous cell carcinomas.

Squamous Cell Carcinoma.

Author: By BruceBlaus (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons Link: https://upload.wikimedia.org/wikipedia/commons/5/5f/Squamous_Cell_Carcinoma.png

Malignant Melanoma

The most dangerous, and fortunately the least common, type of skin cancer is malignant melanoma. These tumors comprise about 5% of the cases of skin cancer. Malignant melanomas originate in the melanocytes. About 1/3 arise from preexisting moles (benign tumors), but most appear spontaneously. These tumors metastasize early and hence are very dangerous. They should be treated aggressively as soon as they are detected by surgical removal, including removing significant amounts of the surrounding tissue, followed by radiation and chemotherapy if there is evidence of metastasis. The 5-year survival rate for those whose tumor has undergone metastasis before it is removed is only around 10%. Since malignant melanoma is so dangerous it is important to know the early warning signs, especially how to distinguish a melanoma from a harmless mole. To help differentiate melanomas from moles we use the ABCDE rule.

A = asymmetry. Moles tend to be symmetrical and can be divided into two mirror-image halves. Melanomas, on the other hand, are asymmetrical and do not exhibit symmetry.

B = border. Moles have very distinct borders while the borders of melanomas are more diffuse and harder to delineate.

C = color. Moles tend to be uniform in color, usually black or brown. Melanomas are usually multicolored with black, brown, reds and/or yellows appearing together in the growth

D = diameter. Any growth greater than 5 mm in diameter is suspect (5 mm is about the diameter of your pencil eraser.

E = evolution. Melanomas are constantly changing, they get larger, change color, change shape and may even bleed. A mole usually does not change.

Look at the examples of malignant melanomas.

Melanoma. Author: National Cancer Institute [Public domain], via Wikimedia Commons Link: https://upload.wikimedia.org/wikipedia/commons/6/6c/Melanoma.jpg