Skin Cancer (Non-Melanoma): Introduction

Approved by the Cancer.Net Editorial Board, 07/2019

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Non-Melanoma Skin Cancer. Use the menu to see other pages. Think of that menu as a roadmap for this complete guide. 

About the skin

The skin is the body’s largest organ. It protects the body against infection and injury and helps regulate body temperature. The skin also stores water and fat and produces vitamin D.

The skin is made up of 3 main layers:

  • The epidermis. The outer layer of skin.

  • The dermis. The inner layer of skin.

  • The hypodermis. The deep layer of fat.

See the Medical Illustrations section for a drawing of these layers.

About skin cancer

Cancer begins when healthy cells change and grow out of control, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread.

Doctors diagnose skin cancer in more than 3 million Americans each year, making it the most common type of cancer. If skin cancer is found early, it can usually be treated with topical medications, procedures done in the office by a dermatologist, or an outpatient surgery. A dermatologist is a doctor who specializes in diseases and conditions of the skin. As a result, skin cancer is responsible for less than 1% of all cancer deaths.

In some cases, skin cancer may be more advanced and require management by a multidisciplinary team that often includes a dermatologist, surgical oncologist, radiation oncologist, and a medical oncologist.  These doctors will meet with a patient, and together they will recommend the best path forward to treat the cancer. In some instances, the surgical oncologist will recommend a surgery to be performed in an operating room because the procedure to treat the cancer is too extensive for an office setting.  Other times, radiation therapy and/or treatments using medication given by mouth or by vein are recommended by the team either in place of or in combination with surgery.

Types of skin cancer

There are 4 main types of skin cancer:

  • Basal cell carcinoma. Basal cells are the round cells found in the lower epidermis. About 80% of skin cancers develop from this type of cell. These cancers are described as basal cell carcinomas. Basal cell carcinoma most often develops on the head and neck, although it can be found anywhere on the skin. It is mainly caused by sun exposure or develops in people who received radiation therapy as children. This type of skin cancer usually grows slowly and rarely spreads to other parts of the body.

  • Squamous cell carcinoma. Most of the epidermis is made up of flat, scale-like cells called squamous cells. Around 20% of skin cancers develop from these cells, and these cancers are called squamous cell carcinomas. Squamous cell carcinoma is mainly caused by sun exposure, so it may be diagnosed on many regions of the skin. It can also develop on skin that has been burned, damaged by chemicals, or exposed to x-rays. Squamous cell carcinoma is commonly found on the lips; at sites of a long-standing scar; and on the skin outside the mouth, anus, and a woman’s vagina. About 2% to 5% of squamous cell carcinomas spread to other parts of the body, which makes it more likely to spread than basal cell carcinoma.

  • Merkel cell cancer. Merkel cell cancer is a highly aggressive, or fast-growing, rare cancer. It starts in hormone-producing cells just beneath the skin and in the hair follicles. It is usually found in the head and neck region. Merkel cell cancer may also be called neuroendocrine carcinoma of the skin.

  • Melanoma. Where the epidermis meets the dermis, there are scattered cells called melanocytes. These cells produce the pigment melanin, which gives skin its color. Melanoma starts in melanocytes, and it is the most serious type of skin cancer. For more information about melanoma, visit the melanoma section on this same website.

Basal cell carcinoma and squamous cell carcinoma are generally grouped together and called “keratinocyte carcinomas,” because they begin in a type of skin cell called a keratinocyte. They are also called “non-melanoma skin cancer” to distinguish them from melanoma. Melanoma is treated differently because it is more likely to spread than other skin cancers. Merkel cell cancer frequently is grouped separately from basal cell carcinoma, squamous cell carcinoma, and melanoma, although technically it is considered a non-melanoma skin cancer.

There are a few other, rare types of skin cancer, including cutaneous (skin) lymphomas, Kaposi sarcoma, skin adnexal tumors, and sarcomas, all of which are classified as non-melanoma skin cancers. The rest of this section focuses on the more common non-melanoma skin cancers.

The next section in this guide is Statistics. It helps explain the number of people who are diagnosed with non-melanoma skin cancer and general survival rates. Use the menu to choose a different section to read in this guide.