Skin cancer is a result of abnormal growth of skin cells known as tumors. These tumors typically develop on the areas of the skin exposed to the sun, such as the forearms, neck, and face. However, cancer may develop in other areas as well, making regular physical examinations of the skin important. This cancer is preventable and treatable, so recognizing the following early warning signs can help one seek medical intervention. 

Early signs
Skin cancer can be categorized into basal cell carcinoma, melanoma, and squamous cell carcinoma, each subtype causing unique symptoms. Basal cell carcinoma can be brought on by prolonged exposure to ultraviolet (UV) radiation from the sun. So, basal cell carcinoma is usually observed over the common sun-exposed parts of the body, especially the neck and head. The early signs of this type of skin cancer usually develop as distinct changes in the skin, like a growth or a sore that does not heal. These growths usually have the following characteristics.

1. Shiny, skin-colored bumps
   These generally appear translucent or sometimes pink, pearly white, brown, or glossy black. In many cases, small blood vessels can be seen through these bumps. Sometimes, they may bleed and cause scabbing. Alternatively, white and waxy scar-like lesions may develop with no clear or defined border.
2. Brown, black, or blue lesions
   The lesions are usually a bit raised and have a translucent border. Some lesions may be transparent and have brown spots all over.
3. Scaly patches
   Usually accompanied by a raised edge, the patches grow in size as the cancer progresses. 
4. Melanoma moles
   Melanomas usually develop on the back, arms, face, and legs. In some cases, this type of skin cancer may also develop in other parts, such as the feet, fingernail beds, and palms of the hands. One of the prominent warning signs for this type of skin cancer is the growth of unusual moles, which can usually be identified through the letters ABCDE (asymmetry, border, color, diameter, and evolving):

• The moles will have irregular shapes.
• The moles will have scalloped or notched borders.
• The mole growths will have an unequal color distribution and could be red, blue, black, pink, or white.
• Melanoma moles usually have diameters greater than 1/4 inch or 6 millimeters.
• Over time, the moles will evolve in terms of size, color, or shape. Sometimes, the moles may start to itch or bleed.

The third type, called squamous cell carcinoma, generally develops in the scalp, lips, ears, and over the backs of the hands. It can also develop inside the mouth, on the bottoms of the feet, and in other areas that are not generally exposed to the sun. Some of the early warning signs for this type of skin cancer include the following.

5. Nodules
   A firm bump known as a nodule develops on the affected part of the skin. In most cases, this nodule is the same shade or color as the skin, i.e., tones of red, pink, brown, or black. 
6. Sores
   Here, a flat sore that has a scaly crust can be observed. Further, a new sore may develop over an old sore or scar. 
7. Scaly, rough patches around the mouth
   A scaly and rough patch may grow over the lips. Over time, the patch may become an open sore. Further, a rough patch or sore can develop inside the mouth.