Detecting and Addressing Hard-to-Find Skin Cancers


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Niraj H. Mehta, MD, reviews the areas of the body where skin cancer can be hard to detect, what the skin cancer will look like on those parts of the body, risk factors for those receiving treatment, and follow-up for patients to catch recurrences.

Niraj H. Mehta, MD

Niraj H. Mehta, MD

Not only is the skin the largest organ in the human body, but it is also responsible for the most commonly diagnosed cancer in the United States: skin cancer.1 The most common forms of skin cancer are basal cell and squamous cell cancers, according to the American Cancer Society. Both are overwhelmingly related to sun and ultraviolet exposure and have high cure rates after treatment. These cancers usually appear on the head, neck, and arms (areas usually exposed to sunlight), but they also can occur elsewhere—oftentimes in areas that make them difficult to detect.1

This review focuses on skin cancers that develop in locations on the body that are often hidden from routine skin screening exams or are not as obvious to find. Melanomas of the skin represent a more severe form of cancer, with very different causes and treatment regimens.

Physicians who screen their patients for skin cancer should be aware of the unique challenges, characteristics, and novel treatments for these hard-to-find lesions and skin changes. Every patient with skin cancer should feel that their treatment options are appropriate and tailored to their particular diagnosis, desired outcomes, and long-term prognosis. The most common treatments include the following:

  • Surgery, including excision of the cancerous tissue or Mohs micrographic surgery, which involves section-by-section removal of layers of the skin at the site of cancer until all suspicious cells are felt to be absent.
  • Radiation, including radiation to only the tumor, and daily treatments to optimize cosmesis and functional results. Emerging radiation technologies can more precisely target cancerous and precancerous tissue while sparing nearby healthy tissue.
  • Topical medications and lotions specific for skin cancer care may be indicated, although they rarely yield the durable outcomes of surgery or radiation.

Difficult-to-Detect Areas for Skin Cancer

The following factors can guide diagnosis, treatment, and follow-up care for patients who develop skin cancers in hard-to-detect, hard-to-reach, and hard-to-treat locations.

Cancer of the ear: These cancers can develop on the outer ear or inside the ear canal and are usually detected by dermatologists. They can perform careful inspections of areas that do not receive regular attention during nondermatological skin screenings.

Cancer on the foot: These cancers often develop on the sole of the foot or between the toes—areas of the body that most people and most nondermatology professionals do not carefully examine. This type of cancer can be missed during regular exams and is usually discovered by dermatologists during a thorough skin exam.

Cancer of the eyelid: Discoloration often differentiates this type of cancer from other cancers. Instead of appearing as dark brown/black spots or disfigured moles, these cancers often resemble a pearl or whitish tumor. They can appear anywhere around the eye or on the upper or lower eyelid as a small bump. They’re often confused with a stye or chalazion, common pimples, or abscesses that form on the upper or lower eyelid. 

Cancer of the anal region: Cancers can occur close to the anus, between the fold of the buttocks. This region can be visualized only by another individual and requires spreading the buttocks to allow exposure of the hidden skin.

These same hard-to-detect areas can also give rise to melanoma, which is a more serious form of skin cancer that is more likely to grow and spread. When a melanoma develops deep in the skin and other tissues, it creates pigment-producing melanocytes and can spread throughout the body, including areas not exposed to the sun. Melanomas can emerge on the soles of the feet, palms of the hands, under the fingernail (subungual melanoma), or in nonskin areas such as the eye or throat.

Because of the complexity and unique presentation of melanomas, additional and often more aggressive treatments are typically required, including wider and deeper surgeries and targeted radiation. For more advanced cases, surgery or radiation may be combined with chemotherapy and immunotherapy. The combination of focal radiation and immunotherapy may halt the spread of cancerous cells to other tissues or attack cancerous tissue while sparing nearby healthy tissue. In these hard-to-detect areas, physicians should pay special attention to areas that are discolored, irregular, or growing/changing over time (see ABCDE guidelines below), often in the absence of sun damage.

Consider Risk Factors in Skin Cancer Treatment Plans

When screening and treating patients who develop skin cancer in these hard-to-detect locations, consider the underlying risk factors that may impact treatment and recovery, including the following:

Skin color: Light-skinned, fair-haired, blue-eyed individuals with long histories of sun exposure are at high risk for skin cancer. However, patients of all skin colors and demographics have some level of risk.

Occupation: People who work outside also have a higher risk of skin cancer, especially if they do not wear sunscreen, protective clothing and hats, or ignore standard sun protection guidelines. These workers might includefarmers/agricultural workers, construction workers, gardeners/lawn care workers, public safety workers, truckers, and airline employees.2

Compromised immune system: Invasive and nonspreading skin cancers are most common in patients whose immune systems are compromised. These tend to be patients undergoing chemotherapy, who have been previously treated for cancer, or patients who have received an organ transplant and remain on long-term immunosuppressive therapies.3 Their treatment history and medications they are on can increase their risk of skin cancer, often years after their initial cancer treatment or transplant surgery. In addition, these immune-related cancers are often aggressive and can develop into a more locally advanced presentation than standard sun-exposure skin cancers.

Social determinants: Patients withlimited access to health care and regular preventive screenings because of social determinants are more at risk. Common factors that limit health care access include low socioeconomic status, racial disparities in health care availability, lack of or inadequate health insurance, and underlying physical and mental health challenges that can impair the body’s immune system.

Conduct a Thorough Examination or Refer to a Dermatologist

Regardless of where a skin cancer originates, accepted medical screening guidelines dictate attention to critical factors, known as the ABCDE guidelines:

  • Asymmetry: The area is irregular in shape, with 2 halves that do not match.
  • Border: The area in question is not well defined and presents with uneven, blurred, or notched borders.
  • Color changes: The area in question presents with multiple colors or irregular color patterns (black, brown, tan, red, blue, pearl-like, etc).
  • Diameter: The area in question is usually larger than 1/4 in (the diameter of a pencil eraser).
  • Evolving: The area in question changes over time, grows larger, changes color or shape, itches, or bleeds.

Follow-Up Care for Patients Treated for Skin Cancer

After a patient has been treated for skin cancer, focus on ongoing recommendations and follow-up care while remaining extra vigilant to screen for any changes in the treated area and other at-risk areas on the body. Encourage patients to undergo screenings regularly by a dermatologist. Skin cancers are also the most common site for multiple occurrences, so individuals who have had a single skin cancer should be more vigilant for the remainder of their lives.

The best advice you can offer your patients is to remind them that the most important thing they can do to catch repeat skin cancers is to undergo thorough skin screenings. Doing a thorough skin exam on their own or with the help of a friend/family member every 2 to 4 weeks until their next clinical visit is highly suggested.

Ask patients whether they have anyone at home who can regularly check the original skin cancer site and other hard-to-reach or hard-to-see locations, where another lesion might develop. Suggest that patients add a regular skin screening reminder to their monthly calendar or mobile device. They can perform a self-exam or ask someone else to check for cancers on these out-of-the-way locations: ear (inside and out), bottom of the feet, fingernails, toenails, eyelids, scalp, and buttocks. If you and your patients focus on these high-risk, hard-to-detect areas, you increase the chances of detecting another skin cancer site early.


1. Cancer facts & figures 2022. American Cancer Society. Accessed June 7, 2022.

2. Sena JS, Girão RJ, Carvalho SM, et al. Occupational skin cancer: Systematic review. Rev Assoc Med Bras (1992). 2016;62(3):280-286. doi:10.1590/1806-9282.62.03.280

3. Rangwala S, Tsai KY. Roles of the immune system in skin cancer. Br J Dermatol. 2011;165(5):953-965. doi:10.1111/j.1365-2133.2011.10507.x

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