Skin is the largest organ of the body and serves a multitude of functions. An adult is covered by just under 2 metres squared.

The skin is composed of 3 layers each containing specialised cells:

This provides the barrier against outside forces

This provides strength to the skin via a collagen scaffold and other types of tissues to give the skin its structure.

Subcutaneous Tissue
This contains fat, lymphatics and blood vessels and helps to regulate skin temperature as well as delivering nutrients to the skin.

Skin Overview

Skin Cells

Basal Cells:
These are small cells in the deepest layer of the epidermis which constantly divide pushing older cells towards the surface. When they become cancerous they are called Basal Cell Carcinoma or BCC

These cells which are located between basal cells in the basal layer produce melanin to protect the skin from harmful ultraviolet rays. Sun exposure increases the rate of melanin exposure and is responsible for a ‘tanned’ appearance. Patches of melanin are responsible for birthmarks and age spots. A benign aggregate of melanocytes is called a ‘naevus’ or mole whereas a malignant aggregate is called a Melanoma.

Squamous Cells:
These are located above the basal cell layer and are formed by basal cells that are pushing upwards. As they mature they are called Squamous cells or Keratinocytes and produce a tough protein which protects the skin. When these become malignant they are called a Squamous Cell Carcinoma or SCC.

Merkel Cells:
These are in the basal layer of the epidermis and play some role in sensation. When these become malignant they are called a Merkel Cell Carcinoma.

Your guide to skin cancer

British Association of Plastic Reconstructive and Aesthetic Surgeons
Society of Surgical Oncology
General Medical Council
Royal College of Surgeons