Cancer of the Skin

Skin cancer is a malignant proliferation of skin cells, and includes basal cell carcinoma, squamous cell carcinoma, and melanoma.

Okay, let's actually start with a quick review, the skin is the largest organ in the body and provides important functions like protection, sensory perception, temperature regulation, and vitamin D production.

Its two main layers, the dermis and epidermis, rest upon the hypodermis, or subcutaneous tissue, which is sometimes considered a third layer of the skin.

The hypodermis consists mainly of adipose, or fat, tissue that provides insulation and padding, and loose connective tissue that helps anchor the skin to the underlying muscle.

Above the hypodermis is the dermis, which is made up of connective tissue that allows the skin to contract and stretch with body movements. It also contains hair follicle roots, nerves, oil and sweat glands, immune cells, and blood and lymphatic vessels.

The most superficial layer of the skin is the epidermis. The epidermis is composed of stratified squamous epithelial cells called keratinocytes. The epidermis is divided into five layers, or strata, consisting of these cells. The basal layer, called stratum basale, is the deepest layer. Here, stem cells called basal cells continuously divide and produce new keratinocytes.

As these new keratinocytes are formed, they move upward, pushing older cells toward the surface. In the process, the cells gradually flatten and become keratinized, meaning they fill with a protein called keratin, a strong, waterproof protein that gives skin, hair, and nails strength.

The basal layer also contains melanocytes. These cells synthesize and secrete melanin, the pigment that gives rise to skin color and helps protect against UV radiation.

The next layer, the stratum spinosum, is composed of irregularly shaped skin cells. As they move upward, they begin to flatten and form the third layer, the stratum granulosum. Here, the cells continue to flatten out and die and begin the process of keratinization.

The next layer up is the stratum lucidum, composed of dead, translucent skin cells. This layer is only found in thick skin like the palms of the hands and soles of the feet.

Finally, the stratum corneum is the outermost layer of skin, composed of many layers of flat, dead cells that are continuously shed, or desquamated, and replaced by newer cells from the underlying layers.