It’s just about winter, right? Grey skies galore. At least there’s no risk of skin cancer, eh?

Reality check. UV rays will find you no matter how much cloud there is in the sky. The sun may not be out, but skin cancer risk is at large regardless.

Besides, you don’t actually need the sun to get a melanoma or a carcinoma. And this is where it’s tricky.

We’re routinely advised to keep an eye out for dodgy-looking moles, changes in growths on your skin, and so forth.

Usually we expect skin cancers to take root on the face and necks, legs and arms, and the torso if we’re prone to going about without a shirt.

The problem with that is some skin cancers, including melanomas, grow where the sun doesn’t shine and aren’t so easy to monitor.

In fact, there’s a category of cancers known as ‘hidden melanomas’.

Here are some places on the body to keep in mind.

The soles of your feet

Acral lentiginous melanoma (ALM) is a rare type of skin cancer that presents on the soles of your feet, the palms of your hands and underneath the fingernails and toenails.

Generally, people with fairer skin and blue eyes are at greater risk of melanoma – while people with darker skin are said to be at lower risk of skin cancer.

However, ALM is most commonly found in African Americans, Asians, Pacific Islanders and Hispanics.

Sunshine not to blame

According to a report at Johns Hopkins Medicine, ALM accounts for fewer than 3 per cent of all melanomas. But it’s often discovered too late for effective treatment.

In the African-American population, up to 25 per cent of patients with ALM will die within five years.

The statistics are worse for Asians and Pacific Islanders, where ALM mortality rates are closer to 50 per cent.

ALM usually starts as a flat dark patch that is clearly distinct from the skin around it. But it may sometimes be reddish or orange in colour.

Melanoma under the nail affects mainly the thumb and big toe.

When presenting under the nail, it often starts as a narrow brown to black pigmented band. It is most prevalent in the nail of the thumb or big toe.

These melanomas are under-researched, but it’s believed they’re not caused by exposure to ultraviolet radiation.

The exact cause isn’t known, but it’s believed ALM may be due to pressure, friction, irritation or injury to the area that becomes cancerous.

Inside the body,  from top to bottom

Melanoma is a cancer that develops in melanocytes, cells that produce melanin.

This is the pigment that produces colour in the eyes, hair and skin. Melanoma usually grows on the skin, but it can also grow in mucosal membranes. This is the moist tissue that lines cavities inside the body.

Mucosal melanoma develops in the mucous membrane that lines the nose, mouth, oesophagus, anus, urinary tract and vagina.

Tricky to diagnose

Again, sunlight isn’t the cause. Researchers are also in the dark, making educated guesses as to risk factors.

According to Penn Medicine, possible risk factors may differ according to the area where the disease is present.

Within the head and neck, the risk factors are poor-fitting dentures (which harbour bacteria), smoking and exposure to carcinogens in the environment.

Human immuno-deficiency virus (HIV) is thought to be a possible risk factor for mucosal melanoma within the anus.

Possible risk factors for mucosal melanoma within the vagina include genetic predisposition, viruses, exposure to certain chemicals and chronic inflammatory disease.

Mucosal melanomas are “especially difficult to detect because they can easily be mistaken for other far more common conditions”.

The eyes have it, too

Our eyes, just like our skin, have melanin-producing cells and can develop melanoma.

It’s why we’re encouraged to wear sunglasses. But melanomas can develop inside the eye, where sunlight doesn’t reach.

According to the Cancer Council, ocular melanoma “can be difficult to diagnose as it forms in the part of the eye that isn’t visible to you or others”.

It doesn’t typically cause any signs and symptoms, and is usually detected by an optometrist during a routine eye test.

Symptoms include poor or blurred vision in one eye; loss of peripheral vision; brown or dark patches on the white of the eye; a dark spot on the iris; small specks, wavy lines or ‘floaters’ in your vision’ or flashes in your vision.

The cause of ocular melanoma isn’t known in most cases.

Risk factors include having pale or fair skin; people with blue or green eyes; a family history of melanoma; having a growth on or in the eye; being exposed to UV radiation or certain chemicals at work, particularly through welding.

Risk increases with age.

Even if your eyesight is great, it might pay to get your eyes checked every couple of years.