Having been in practice for many years and treated many patients, there have been some memorable cases. One particular individual that comes to mind I saw only once, a single visit. But I will always remember her, and with some regret. She was an older woman who presented to my office for care of a callus on her foot. This was a mild annoyance to her, not significantly painful, and had been debrided previously a number of times (debrided means, basically, trimming).

Doesn’t sound terribly remarkable, you may be thinking. The callus was found on the ball of one foot, under the big toe joint, and was moderately thick and a little discolored. The other foot had no callus whatsoever, although there are often differences between the left and right foot. I remarked that it was an unusual-looking callus and recommended she have it biopsied to determine if it was, indeed, just a callus. She did not return and I never heard from her again. A few years later, through the grapevine, I learned it was an amelanotic melanoma and she had lost her leg. This is a particularly insidious and deadly skin cancer that is NOT blackened, or even discolored sometimes. Thus, the diagnosis is often made too late.

A frequent topic in the weekly magazines, the ones found in the aisle at the grocery store, is the increasing incidence of skin cancers. Skin cancer is the most common form of cancer, by far. In fact, it is more common than all the other forms put together. One in five Americans will develop skin cancer by the age of 70. More than 5.4 million cases of nonmelanoma skin cancer were treated in the most recent year with good data. Eighty percent of all skin cancers diagnosed will be a non-melanoma type, with most of these being basal cell carcinoma. Yet the great majority of skin cancer deaths are due to melanoma. Nearly 20 Americans die from melanoma every day. In 2019, estimates state 7,230 deaths will be due to melanoma. And the frequency with which melanoma is being diagnosed is increasing annually.

Most of us automatically think of the sun’s dangerous rays as being the source of all skin cancers, secondary to the effects of direct exposure. Skin cancer can develop anywhere on the body, including in the lower extremities. Melanoma, the most serious skin cancer, often develops on sun-exposed skin. Yet, it may also start in places that receive little sun exposure, such as your foot. Because most people never check their feet for signs of melanoma, this cancer often spreads before it’s noticed.

Melanomas may even occur beneath a toenail, of all places. This is most common in the big toes of your feet. The cancerous cells underneath the nais can look like purple, brown, or black bruises. These also may look like dark streaks that grow vertically in the nail. Unlike nail injuries where the nail eventually grows out, these streaks don’t go away. Many people will assume these changes are fungal in origin, another good reason to have nail changes evaluated by a specialist.

Melanomas may also occur on the soles of the feet, an area few of us look at even occasionally. And generally, since the feet are not well examined during routine medical exams, lesions here are diagnosed much later than desirable. A new study concludes daily wear-and-tear seems to promote skin cancer in the feet because of the stress endured by the skin on the sole. Physical pressure and irritation to the skin is known to encourage the development of a cancerous lesion. Thus, the damage caused by walking and running may be enough to encourage the development of melanoma on the bottom of the feet.

The most important factor in the development of skin cancer, besides sun exposure, is genetic predisposition, like being fair-skinned, having light hair, or blue eyes. People with these characteristics are burned by sun exposure easier since they produce less melanin, which is the protective pigment that absorbs certain forms of radiation. The effect of melanin is to reduce the amount of damage incurred by the cells of our skin. Some other known risk factors for melanoma include having a history of at least one severe sunburn before the age of 18, having preexisting moles on your feet, having at least 50 moles throughout your body, or having a family history of melanoma or another type of skin cancer.

Environmental factors increase the risk for developing skin cancer as well. Oral cancers are more common in heavy drinkers and smokers. Environmental pollutants, chemical burns, motor vehicle exhaust, all can cause skin damage that increases the likelihood of developing skin cancer, regardless of a person’s history of sun exposure and skin type.

Statistically, most skin cancers are either basal cell or squamous cell carcinoma. But melanoma is well known to be the most serious and deadly form of skin cancer. This type develops in the melanocytes, the cells that produce melanin. Melanoma may spread from the melanocytes to other parts of your body. The prognosis with melanoma is primarily a factor of how early it is detected. The later in the tumor’s growth it is diagnosed, the poorer the prognosis. Non-surgical treatments are rarely effective. As a melanoma grows and extends into deeper into the tissues, it is more likely to spread through the lymphatics and blood vessels, becoming ever more serious, and ever deadlier. If melanoma spreads into lymph nodes, there is a 23 percent survival rate.

One relatively uncommon form of melanoma is usually unrelated to sun exposure, termed acral lentiginous melanoma (ALM), it is most often found on the palms of the hands, soles of the feet, and under the nails. ALM can be fast-moving and dangerous because it is frequently discovered later, remaining undetected until the cancer has spread to other areas of the body.

Exactly how is skin cancer diagnosed? Do an inspection! If you notice a mole, bump, or patch on the skin that meets the “ABCD’s” of melanoma, see a physician immediately. These criteria are: asymmetry (if the lesion is divided in half, the sides don’t match), the borders look uneven or ragged, there is more than one color (often with an uneven distribution), and, lastly, the lesion is wider than a pencil eraser (greater than 6 mm). To detect other types of skin cancer, look for non-healing sores, bumps that crack or bleed, have “donut-shaped” edges, or scaly areas.

As to prevention, these are items that most of us are aware of. Sun tan lotions are clearly beneficial in reducing the amount of exposure to harmful radiation, but who remembers to apply sunscreen to the skin of the feet? Reduce direct sun exposure, especially between 10 a.m. and 4 p.m. Don’t get sunburned, if in any way avoidable. Avoid tanning (and never use tanning beds). When out in the sun, wear protective clothing such as a broad-brimmed hat.

The key to treatment is early diagnosis. Allowed to spread, melanoma can turn deadly. By checking your feet and other areas, you can find it early when it’s highly treatable. A regular evaluation is important to check for abnormalities that might point to an evolving skin cancer. If appropriate, a podiatrist or dermatologist will perform a small biopsy of the lesion which will definitively identify the type of lesion. The most common forms of skin cancer are highly curable if detected early. The take-home message? Keep an eye on your skin and have anything suspicious checked out. Certainly in this situation, ignorance is not bliss, it’s dangerous.

Editor’s note: Dr. Conway McLean is a physician practicing foot and ankle medicine in the Upper Peninsula, with a move of his Marquette office to the downtown area. McLean has lectured internationally on wound care and surgery, being double board certified in surgery, and also in wound care. He has a sub-specialty in foot-ankle orthotics. Dr. McLean welcomes questions or comments atdrcmclean@outlook.com.