Squamous cell carcinoma is a common type of skin cancer that develops from the squamous cells in the outer layer of the skin.

It tends to grow more quickly than basal cell carcinoma and, in some cases, can spread to other parts of the body if left untreated. Because of this, early recognition and medical assessment are important.

A squamous cell carcinoma can appear in several different ways, but it typically develops on areas exposed to the sun.

Common features include:

• a thickened, scaly patch of skin
• a firm, raised lump
• a sore that crusts, bleeds, or does not heal
• a bump that becomes tender or painful
• a spot that continues to grow over weeks to months

Unlike many benign (harmless) spots, squamous cell carcinomas tend to persist and gradually enlarge.

Squamous cell carcinomas most commonly occur on sun-exposed areas, including:

• the face, especially the lips, ears, and nose
• the scalp, particularly in people with thinning hair
• the backs of the hands and forearms
• the lower legs

It can also develop in areas not typically exposed to the sun, although this is less common.

Risk increases with cumulative sun exposure over time.

Factors that increase risk include:

• fair skin that burns easily
• long-term sun exposure
• outdoor work or recreation
• increasing age
• a history of previous skin cancers
• a weakened immune system

People who have had one squamous cell carcinoma are more likely to develop others.

The main cause is ultraviolet radiation from the sun. Over time, UV exposure damages skin cells and can lead to the development of skin cancer.

Chronic sun damage, often seen as rough or sun-damaged skin, increases the risk.

Squamous cell carcinomas can grow more quickly than some other skin cancers and, in certain cases, can spread if left untreated.

Early assessment can:

• reduce the size of the lesion before treatment
• simplify treatment and recovery
• lower the risk of spread
• prevent ongoing pain, bleeding, or ulceration

A lesion should be assessed by a doctor if you notice:

• a scaly lump that continues to grow 
• a sore that bleeds, crusts, or does not heal
• a constantly tender or painful skin lesion
• any abnormal enlarging change in a sun-exposed area

These signs do not always indicate cancer, but they should be checked promptly.

Squamous cell carcinoma cannot be reliably diagnosed from photos alone.

While images may help document changes, they are not sufficient to confirm a diagnosis. Many benign skin conditions can look similar.

An accurate diagnosis requires an in-person examination. In most cases, a biopsy or removal is needed so the tissue can be examined under a microscope.

Treatment depends on the size, location, and depth of the lesion.

Treatment may include:

• surgical excision
• superficial radiotherapy
• curettage and cautery in selected cases
• topical treatments for very early lesions

Surgical removal is often the main treatment, particularly for lesions that are thicker or located in higher risk areas.

Squamous cell carcinoma often develops in areas of long-term sun damage. The surrounding skin may appear rough, dry, or scaly.

Actinic keratoses, which are rough, sun-damaged patches, can sometimes develop into squamous cell carcinoma over time.