Types of non-melanoma skin cancer

Non-melanoma skin cancer is a group of cancers that can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body, but this is rare for most non-melanoma skin cancers.

There are 2 main types of non-melanoma skin cancer – basal cell carcinoma (BCC) and squamous cell carcinoma (SCC).

BCC is the most common type of skin cancer. It makes up about 75%–80% of all skin cancers.

BCC starts in basal cells of the skin, which are round cells found in the top or outer layer of the skin (epidermis). BCC tends to grow slowly. It is rare for BCC to spread to other parts of the body, but it may grow into nearby tissue if left untreated.

The most common place for BCC to develop is on the head, face and neck. It is most often diagnosed in people who are middle-aged or older, but it can also develop in people who are younger.

There are several subtypes of BCC. The following are the main subtypes.

Nodular BCC is the most common subtype. It usually develops on areas of the face exposed to the sun. Nodular BCC appears as a round, raised, pink, red or pearly white lump or an area with wide blood vessels showing on top.

Superficial BCC is the 2nd most common subtype. It usually develops on the central part of the body (trunk), arms or legs. Superficial BCC appears as a pink or red scaly area.

Infiltrative and micronodular BCCs usually develop in the head or neck area. They grow deeper into the skin and into the inner layer of the skin (dermis). Infiltrative and micronodular BCC can look like nodular BCC. They grow and spread more quickly than nodular and superficial BCC.

Morpheaform BCC usually develops in the head or neck area. It appears as a flat, firm white or yellow area. Morpheaform BCC can look like a scar. It grows and spreads more quickly than nodular and superficial BCC. Morpheaform BCC may also be called sclerosing BCC or fibrosing BCC.

SCC is the 2nd most common type of skin cancer. It makes up about 20% of all skin cancers.

SCC starts in squamous cells of the skin, which are flat cells found in the outer part of the epidermis. SCC usually grows slowly, but it grows more quickly than BCC. It is also more likely than BCC to grow deeper into the skin and spread.

When SCC is found very early and only in the epidermis, it is called SCC in situ. It isn’t usually life-threatening because it is an early form of SCC. SCC in situ may turn into invasive SCC if not treated. This means that the cancer can grow into nearby tissue or deeper layers of skin. SCC in situ is also called Bowen’s disease or intraepidermal SCC.

SCC usually develops on areas of skin exposed to the sun. Less often, it can develop on injured or inflamed areas of skin, such as scars, burns and sores or ulcers that don’t heal. SCC can also develop on the skin around the anus and vagina.

There are subtypes of SCC, such as desmoplastic SCC and adenosquamous carcinoma of the skin. They tend to have a high risk of the cancer coming back after it has been treated (recurrence).

Keratoacanthoma is a tumour that looks very much like SCC. It tends to develop and grow quickly then suddenly shrink without any reason (spontaneous regression). This happens over a short period of time, usually a few weeks or months. It is treated like SCC so it is sometimes considered a subtype or variant of SCC.

The following non-melanoma skin cancers are rare. They make up about 1% of all skin cancers.

• Merkel cell carcinoma
• cutaneous T-cell lymphoma
• Kaposi sarcoma
• soft tissue sarcomas, such as dermatofibrosarcoma protuberans and angiosarcoma
• microcystic adnexal carcinoma (sweat gland cancer)