1st Revision: Isobel Lester There are several types of cancer affecting the feet and toes, but the most common type is melanoma. This is the most serious skin cancer, most often due to sun exposure. This will be the focus of this article. Because of its location and its perceived lack of exposure, cancer on the skin of the foot can go unnoticed for quite some time until it is fairly advanced and has often spread, which helps account for the disproportionately high mortality rate. Famously, the singer Bob Marley died as a result of undiagnosed foot melanoma.
What is foot cancer?
Most foot tumours are benign (non-cancerous); usually, synovial cysts (30% of all foot tumours) and lipomata are seen on the top surface (dorsum) of the foot. On the sole of the foot, the most common benign tumours are villonodular synovitis (or tenosynovial giant cell tumours), deep-seated lesions, and plantar fibromatosis or epidermal inclusion cysts.
Types of malignant (cancerous) tumours in the foot can be split into two main groups: skin cancers and non-skin cancers. The latter group is very rare up to the age of 40 years and include the bone cancers Ewing’s sarcoma and osteosarcoma. In adults over 40 years old, chondrosarcoma (which begins in the cartilage cells) is relatively common.1
Other common cancers of the feet are include skins cancers like melanoma, squamous cell carcinoma (which is the most common), and basal cell carcinoma. Squamous cell carcinoma is usually confined to the skin and does not spread, but can become more aggressive when advanced and metastasise and spread throughout the body. Basal cell carcinoma (BCC) is often seen on UV-exposed skin. One of the least aggressive cancers, BCC causes localised damage but rarely spreads to other sites.
According to Medical News Today, foot melanoma can appear anywhere on the foot, including under the nail or on the sole of the foot. 3-15% of melanomas appear on the foot. Malignant melanoma accounts for most skin cancer deaths, yet makes up only 1% of skin cancers.
There are several subtypes of melanomas:
- Acral lentiginous melanoma: around 50% of all cases of foot melanoma. This type of melanoma disproportionately affects darker-skinned people. In the early stages, it can be hard to identify, seen as a darker patch of skin or a streak in a toenail.
- Nodular melanoma: typically seen as a dark blue-black or red papule. This is the type most likely to develop in older adults and develops relatively quickly. Nodular melanomas rapidly grow inwards towards the body’s other tissues and organs. They commonly bleed or ooze (NHS).
- Superficial spreading melanoma: this is the most common melanoma. It grows outward across the skin rather than inward towards the body’s organs and systems. Most are usually encountered on the top of the foot.
- Amelanotic melanoma: these are colourless and may resemble ordinary flesh. As a result of this, when they occur on the foot, they may be misdiagnosed.
Signs and symptoms of foot melanoma
Key preventative measures with all skin cancers are avoiding sun exposure and self-surveillance, noticing new skin blemishes and watching existing ones for changes in shape, colour, etc. The first sign of melanoma may be a change in an existing mole. However, it may also present as a new mole, although most moles are completely harmless. The whole foot should be examined, including beneath the toenails and between the toes.
Sometimes, a melanoma lesion can form on the skin and then disappear. However, the cells may still travel through the body and cause cancer to develop elsewhere. Spotting changes in moles is crucial to catching melanoma early.
Two simple checklists can help track changes in moles:
- The acronym ABCDE is for all moles:
Asymmetry: the lesion isn’t identical on both sides.
Border: the lesion has a ragged, irregular or indistinct edge.
Colour: the lesion is not all the same colour.
Diameter: the lesion is wider than 6 millimetres.
Evolution: the lesion has gradually changed in size, shape, or colour.
If a person notices any of these features, it is important to see a doctor.
- CUBED is an acronym specifically for foot melanoma, which would usually be seen on the sole or under the toenail:
Coloured: a lesion is a colour different to the surrounding skin.
Uncertain: a lesion has not had a definitive diagnosis.
Bleeding: a lesion bleeds or leaks fluid.
Enlargement: a lesion gets bigger or worsens despite treatment.
Delay: the lesion takes more than 2 months to heal.
Other warning signs for foot melanoma might include:
- A sore/lesion that does not heal or is healing very slowly.
- Brown or black vertical line under the toenail.
- Pinkish-red spot or growth.
- New spot or growth where you injured your foot.
- Rapidly growing mass on your foot, especially in a place where you once injured your foot.
- Sore that looks like a diabetic ulcer.
- Pigmentation spreading from the border of the lesion to surrounding skin.
- Redness or new swelling beyond the border of a lesion.
- Changes in sensation, such as itchiness, tenderness, or pain.
If two or more of the above symptoms are present, your doctor will refer you to a skin cancer specialist for in-depth assessment. Diagnostic tests, aside from the assessment of family history and the changes in the lesion’s size and appearance, will examine the approximate age of the lesion, any other suspicious moles or blemishes, and lymph nodes in the region of the mole. If the doctor suspects that the lesion is melanoma, they will refer the individual to a dermatologist. They will closely examine the mole or lesion using a dermatoscope, and they will perform a biopsy (collect a sample) of the lesion if they think it is necessary.
There are several types of biopsy, all done under local anaesthetic, depending on the affected area and size of the lesion:
- Shave biopsy: uses a sharp blade to remove the lesion of interest. It heals with a scar and does not require sutures.
- Punch biopsy: uses a “cookie-cutter” tool to take a sample of all skin layers, including the layer under the skin. They will usually place a temporary suture to close up the biopsy site.
- Incisional or excisional biopsy: involves removing part, or the entirety, of a mole and sending it for microscope examination. This is the preferred method for assessing suspected melanomas.
A doctor may order further tests, such as surgical evaluation, to check a nearby lymph node for involvement, in case the cancer has spread. A biopsy can identify cancerous cells, which type of cancer is present, and assess the thickness of a tumour. If melanoma has not spread, it is called stage 1 cancer. Diagnosing cancer at stage 1 greatly increases the chance of successful treatment.
Risk factors for foot cancer
Sunburn, an inflammatory reaction to the ultraviolet (UV) radiation in sunlight, is the leading cause of squamous cell carcinoma, basal cell carcinoma, and melanoma.
These are the main risk factors for melanoma, aside from sun exposure:
- Having fair skin
- Sun-sensitivity (e.g. burning easily)
- Having pre-existing moles on feet
- Having at least 50 moles on the body
- History of severe sunburn before age 18
- Family history of skin cancer
The main risk factors for bone cancer of the foot include:
- have had previous exposure to radiation during radiotherapy
- have a condition known as Paget's disease of the bone – however, it is rare to develop cancer
- have a rare genetic condition, called Li-Fraumeni syndrome – people with this condition have a faulty gene that ordinarily helps stop the growth of cancerous cells
Treatment of foot cancer
The treatments available for foot melanoma depend on the stage the cancer has reached and your overall state of health. If caught early enough (stage 0-1), the mole and surrounding skin may simply be removed (excision); however, the anatomy of the foot is extremely complex, making surgery difficult if the cancer has penetrated the tissues.
For more advanced cancer, the treatment options are chemotherapy with cytotoxic drugs, immunotherapy that stimulates the immune system to attack the cancer cells, radiation therapy, or an operation called a lymphadenectomy that removes the surrounding lymph nodes. Bone cancers in the foot are typically resolved by removing the affected bone, treatment via chemotherapy and radiation therapy.
FAQ’s
- Is toe cancer curable?
- Foot melanoma is often treatable in its early stages (especially stage 0). However, diagnosis usually happens during the later stages, as early on, the symptoms may not be readily noticeable. If foot melanoma spreads or metastasizes, it can be life-threatening.
- How is toe cancer treated?
- This depends on the stage of the cancer. Typically, removal of the tumour (stage 0) or chemotherapy, and radiation therapy or immunotherapy for more advanced cancer. The affected lymph nodes may also be removed.
- What does cancer look like on your feet?
- Foot melanoma could look like a brown, blue-black or pinky-red mole or patch on the skin or a vertical brown or black line under the nail (aad.org).
- How does foot cancer start?
- Most foot melanomas start because of exposure to U.V. light (mainly from the sun). Family history also plays a role.
- Can you have melanoma for years and not know?
- Yes, this is the reason why many lesions are not caught early enough to be easily treated.
- How do you know if you have cancer in your toes?
- Moles or discoloured patches between the toes or dark vertical lines under the nail.
- Can you get cancer in your toes?
- Yes, the toes are just like the rest of your foot. In fact, they often receive more sunlight in shoes like flip-flops or sandals.
- How common is cancer in the foot?
- Cancer of the foot is relatively rare (but see risk factors above), and as many as 50% are initially misdiagnosed.
