Skin cancer is a debilitating disease caused by the growth of cells in a disorderly manner. The multiplying cells--especially cancerous ones--can spread to other parts of the body through a process called metastasis. To scientists, the branched-out cells look exactly the same as those in the skin. However, given that cancer is named on the basis of the place where it starts, benign cells that spread from the skin to the other body parts will be still called skin cancer cells.

That brings us to the conclusion that skin cancer isn't limited to the skin. As per a report published by MD Anderson Cancer Center, melanoma or skin cancer cells originate in melanocytes, the substance that causes skin pigment. When they make their way to other body parts, they are called noncutaneous melanomas which aren't caused by UV rays emitted by the Sun or heredity, as normally perceived.

The study has listed the surprising sites where noncutaneous melanomas can form and they are as follows:

1. Ocular (eye)

The insides of the eye or the irises have melanin-producing cells and therefore can develop melanoma. Most ocular melanomas are difficult to spot by looking into a mirror and they don't cause early symptoms, according to Mayo Clinic.

2. Mucosal (of the mucous membranes)

Mucosal melanoma occurs in the mucous membranes, the soft tissue that lines organs and other areas in the body such as the head and neck region, lips and mouth, anorectal region (anus and rectum) and vulvovaginal region (vagina and vulva). Mucosal melanoma typically affects people aged 70 and older, according to Cleveland Clinic.

3. Under the fingernails

Doctors say gel nails have more odds than aesthetics. Cancerous growths under the fingernails are largely associated with the gel nail trends as part of which a UV device is used for quick-drying. The electrical device, that act as a tanning bed for the nails, can facilitate the growth of melanoma, Stephen Stahr, MD, a dermatologist in New Braunfels, Texas, told The Healthy.

4. In the gluteal cleft

Gluteal cleft, vernacularly known as butt cracks, are also the sites where melanoma can develop. Non-lethal cancer, called squamous cell carcinoma, can form in the site, Readers Digest reported, citing Stahr.

5. On the scalp

The scalp is one of the most common places for melanoma growth. However, their sight can be obscured by the hair, or the itching or burning sensation can be mistaken for dandruff, Dr. Stahr said.

6. In the ear canal

Stubborn crustiness inside the ear canal can be melanoma, Bobby Awadalla, MD, a dermatologist and CEO of UVO, told Readers Digest. When the gunk doesn't go by repeated scrubbing or washing, it surely points to cancer.

7. Underneath the tongue

Melanoma can develop under the tongue, which is why dentists take a closer look at the area for any suspicious growth during clinic visits. Even as the area isn't exposed to the sun as much, it is possible that cancer metastasized from a different site.

Experts have linked a 99% survival rate with the early detection of melanoma. Guilherme Stecanella/Unsplash