Skin Cancer: Atypical Locations
Reviewed by: HU Medical Review Board | Last reviewed: May 2017. | Last updated: January 2021
The majority of skin cancers develop in locations with frequent sun exposure: face, neck, ears, chest, back, arms, and legs. Yet some skin cancers grow in non-sun exposed areas. These atypical or unusual locations include the nails, palms of the hand, soles of the feet, eyes, vulva, or anus.
Fingernails and toenails
Melanoma of the nail
Nail melanoma may look like a dark band running down the length of the nail. The thumb or great toe are most likely to be affected.1 Dark bands can be harmless, especially if they appear on multiple nails.2 However, a change in appearance is worrisome. Changes to look for include:
- Width more than 3 mm
- Pigmentation that goes into the cuticle or past the side edge of the nail
- Change in the look of the nail
Nail melanoma accounts for about half of melanomas in people with dark skin tones.2 It is most likely to be diagnosed after age 50 years.1 If your close blood relative has had melanoma, you are at greater risk of melanoma, including nail melanoma.2 There may be a link between previous nail injury and development of melanoma.
Another word for nail melanoma is “subungual melanoma.” Subungual melanoma is a subtype of acral lentiginous melanoma. Acral lentiginous melanoma usually develops on the palms, soles, or joints such as knees and heels. It is described in more detail below.
Squamous cell carcinoma of the nail
SCC and its early form, Bowen disease, can grow within the nail unit.2 Nail SCC can be hard to identify because it does not look like other SCCs. It is usually a red, rapidly growing mass that interrupts normal nail growth.2 Providers and patients may mistake it for a wart, fungal infection, or amelanotic melanoma. Because it is difficult to recognize, nail SCC is often diagnosed late.1
Treating nail cancer
SCC that grows on the fingers and in the nail unit may be treated with Mohs surgery or amputation.2 Melanoma is often treated more aggressively with excision or amputation.3 If it is necessary to remove a finger or toe, your surgeon will save as much healthy tissue, length, and sensation as possible.4
Palms and soles
Melanoma that grows on the palms of the hands or soles of the feet is called acral lentiginous melanoma. This type of melanoma also can affect the finger tips, knuckles, elbows, knees, and ears.5 Subungual melanoma, described above, is a subtype that affects the nails.
On the palms and soles, melanoma may look like a dark bruise with an irregular border and mix of colors.4 The lesion is usually black, brown, or blue-black. In rare cases, it is colorless (unpigmented). It usually does not cause any symptoms.4
Acral lentiginous melanoma is the most common type of melanoma in black Americans. It makes up 36% of melanomas among blacks, 18% in Asian/Pacific Islanders, 9% in Hispanic whites, and only 1% in non-Hispanic whites.6 This type of melanoma is not related to sun exposure.7 Some studies have shown a link between injury to the area and acral lentiginous melanoma.6
Acral lentiginous melanoma is often diagnosed late.6 It can be hard to see the bottom of your feet, so the lesion may go unnoticed.4 Additionally, the lesion may be misdiagnosed as a fungal infection, wart, or injury.4 By the time it is correctly diagnosed, it may have advanced. For this reason, survival rates are lower than other melanomas.6
Acral lentiginous melanoma is treated with wide local excision. Plastic surgery can improve the appearance and function of your hand or foot after the cancer is removed.4 If the cancer is deep, your doctor will do a sentinel lymph node biopsy to see how far it has spread.4
Melanoma of the eye is the most common eye cancer, although eye cancer itself is very rare.8 An estimated 3,130 new cases of eye cancer will be diagnosed in 2017, which is less than 0.2% of all cancers in the United States.8 Another name for melanoma of the eye is intraocular melanoma.
More than 85% of eye melanomas affect the uvea, the middle layer of the eye.9 The risk factors for eye melanoma are similar to other melanomas: fair skin, light-colored eyes, older age, male gender, and certain inherited conditions.8,10 It is not known whether sun exposure is a risk factor for eye melanoma.8,9
About 30% of people with eye melanoma have no symptoms.9 Those people who do have symptoms may experience:9
- Blurry visions
- Light flashes in the eye (photopsia)
- Visual field reduction
The goals of eye cancer treatment are to remove the cancer and save as much vision as possible.10 The first choice of treatment is called brachytherapy.9 This treatment involves attaching a small disc, called a plaque, to the eye. The plaque has radioactive seeds. The plaque is left in place for several days and then removed.11 Surgery is an option for larger tumors and when it will be hard to save any vision.9 The word for surgical removal of the entire eye is enucleation. The 5-year survival rate for eye cancer is 80%.8 Metastasis is common with eye cancer: 50% of patients will have cancer metastasis within 15 years.12
The vulva is the outer part of the female genitals. SCCs and melanoma can develop on the vulva.13 Vulvar cancer is uncommon. There will be an estimated 6,020 new cases in 2017.8 Women are most likely to be diagnosed in their 60s.14 About 90% are SCC and 6% are melanoma.13
Nearly 70% of vulvar cancers are related to human papilloma virus (HPV) infection.8 HPV is a group of viruses that can cause warts.13 Usually these warts are harmless and do not lead to cancer. However, some strains of this virus have been linked to SCC. HPV can be spread through sexual contact.
The symptoms of vulvar cancer are similar to symptoms of other conditions that affect the genitals. They include:13,15
- Sores, lumps, or bumps on the vulva
- Changes in the color or appearance of the vulva
- Itching, burning, and bleeding/discharge
- Pain, especially when urinating or during sex
Vulvar SCC is treated with surgery, radiation therapy, and chemotherapy. Treatment is selected with the goals of removing the cancer and maintaining sexual function to the extent possible.13 The 5-year survival rate for vulvar cancer is 72% overall.16 When the cancer is caught early, the 5-year survival rate is 86%.16
Most anal cancers are SCC.17 The cancer develops in the anal canal or in the skin just outside the anus, called the anal verge. The anal canal connects the rectum to the anal opening. Basal cell carcinoma can develop in the skin around the anus. Anal melanoma is rare, but often advanced when it is discovered.
An estimated 8,200 cases of anal cancer will be diagnosed in 2017, comprising about 0.5% of all cancers in the United States.8 Anal cancer is more common in women than men.8,18 The median age at diagnosis is 60 years.18 HPV infection is a strong risk factor for anal SCC.8,18
About 20% of people with anal cancer do not have any symptoms.18 The symptoms of anal cancer overlap with the symptoms of many other conditions. The main symptoms are rectal bleeding and pain.18 Other symptoms include:19
- Itching, abnormal discharge
- Lump or mass
- Feeling of fullness
- Changes in bowel movement
- Swollen lymph nodes
The first choice of treatment for anal cancer is radiation therapy with chemotherapy. This combination is called chemoradiation.17,18 The 5-year survival rate for anal cancer is 66% overall.19 When the cancer is caught early, the 5-year survival rate is 81%.19