Skin cancer can and does develop on the buttocks, even though this area rarely sees direct sunlight. Basal cell carcinoma, squamous cell carcinoma, melanoma, and several rarer malignancies have all been documented in the gluteal region. The cases are uncommon compared to sun-exposed sites like the face and arms, but they present a distinct clinical challenge: because neither patients nor doctors expect to find cancer there, tumors on the buttocks tend to be caught later and sometimes misdiagnosed as cysts, rashes, or scars.
Basal Cell Carcinoma on the Buttocks
Basal cell carcinoma is the most common skin cancer overall, but finding one on the buttocks is genuinely unusual. A review of cases in the literature found that only about 28 patients had been described with basal cell carcinoma of the buttock, and the calculated prevalence among all basal cell carcinomas was roughly 0.35%.1PubMed. Basal Cell Carcinoma of the Buttock A separate ten-year analysis of biopsied basal cell carcinomas found 53 tumors on the groin or buttocks out of all cases, accounting for less than 0.1% of the total. The buttocks were the most common location within that group, and the nodular subtype dominated.2PubMed. Basal cell carcinoma of the groin and buttocks: a clinical and histological analysis of a rare presentation of a common tumor
What makes these cases especially interesting is that the patients largely did not have traditional risk factors for basal cell carcinoma. None of the patients in the ten-year analysis had genetic syndromes prone to skin cancer or were immunosuppressed.2PubMed. Basal cell carcinoma of the groin and buttocks: a clinical and histological analysis of a rare presentation of a common tumor This suggests that while ultraviolet radiation is the dominant driver of basal cell carcinoma on the head, neck, and arms, other mechanisms may be at work in sun-protected areas. The tumors typically showed up as painless nodules, which is easy to dismiss as a benign lump or ingrown hair in a region you cannot easily see yourself.
Melanoma in Sun-Protected Areas
Melanoma is the skin cancer people fear most, and there is a widespread assumption that it only strikes skin that gets heavy sun exposure. The relationship between sunlight and melanoma is real: studies have found that the distribution of melanocytic nevi and cutaneous malignant melanoma across the body surface is broadly consistent with sun exposure patterns.3Acta Dermato-Venereologica. Melanocytic naevi, melanoma and sun exposure But “broadly consistent” is not “exclusively.” Melanoma occurs on the soles of the feet, under fingernails, on the scalp beneath thick hair, and on the buttocks. When it shows up in sun-protected locations, ultraviolet light alone cannot explain it.
There is growing evidence that genetic and epigenetic factors play a significant role in melanoma development independent of sun exposure. Research into non-sun-related risk factors has identified links between melanoma susceptibility and multiple genes, as well as unexpected connections to certain neurological conditions and embryonic development pathways.4PubMed Central. It’s Not All Sunshine: Non-sun-related Melanoma Risk-factors In other words, your genetic makeup can put you at risk for melanoma even in places where the sun has never reached. This is part of why dermatologists emphasize checking your entire body, not just the spots that get tanned or burned.
One epidemiological study examined whether wearing bikinis during adolescence raised trunk melanoma risk. The results were nuanced: bikini use itself was not significantly associated with trunk melanoma, but frequent outdoor swimsuit use was strongly associated with increased melanoma risk among sun-sensitive women, while sun-resistant women who tanned easily appeared to have a lower risk.5American Journal of Epidemiology. Melanoma and the Sun: The Effect of Swimsuits and a “Healthy” Tan on the Risk of Nonfamilial Malignant Melanoma in Women The takeaway is that even on areas partially covered by clothing, melanoma risk is driven by a mix of individual susceptibility and cumulative exposure history rather than by whether a specific patch of skin happened to catch the sun on a given day.
When Chronic Wounds Turn Cancerous
Squamous cell carcinoma on the buttocks sometimes arises through a pathway that has nothing to do with sunlight or genetics. Chronic, non-healing wounds and long-standing scars can undergo malignant transformation into what is called a Marjolin’s ulcer, a squamous cell carcinoma that develops in damaged tissue. This is especially relevant for people with spinal cord injuries, who are prone to pressure ulcers on the buttocks from prolonged sitting or lying.
A case report described a 41-year-old paraplegic man who was admitted for a non-healing ulcer on the lower portion of his left buttock. A biopsy revealed squamous cell carcinoma.6Indian Journal of Physical Medicine & Rehabilitation. Chronic Wound to Marjolin’s Ulcer: A Threatening Complication This type of cancer tends to develop over years or decades in tissue that has been repeatedly injured and scarred. For anyone caring for a person with chronic pressure sores, or for someone living with a wound that refuses to heal, this is a reason to have persistent ulcers biopsied rather than simply treated with wound care indefinitely.
HPV and Perianal Skin Cancer
Human papillomavirus, the same family of viruses linked to cervical and throat cancers, is also a recognized risk factor for skin cancer in the anal and perianal region, which sits right at the boundary of the buttocks. A prospective study found that people who tested positive for HPV 16 had about three times the risk of developing anal and perianal skin cancer, while those positive for HPV 18 had roughly four times the risk.7British Journal of Cancer. Human papillomavirus infection as a risk factor for anal and perianal skin cancer in a prospective study
This is a non-UV pathway to skin cancer that is entirely plausible on the buttocks. HPV is transmitted through skin-to-skin contact, and the perianal area is a common site for infection. Vaccination against HPV, which is widely recommended for adolescents and young adults, targets the high-risk strains involved. For people who are already beyond the typical vaccination age or who have known HPV exposure, awareness that this virus can cause cancer in the gluteal area is worth having.
Rarer Malignancies That Show Up There
Beyond the “big three” of basal cell, squamous cell, and melanoma, several uncommon cancers have a documented affinity for the buttock region.
Merkel cell carcinoma is an aggressive neuroendocrine skin cancer most often found on the head and neck. About 5% of cases occur on the buttocks.8PubMed Central. An unusual presentation of Merkel cell carcinoma: a case report This cancer is driven partly by ultraviolet radiation and partly by infection with Merkel cell polyomavirus, which is linked to up to 80% of cases.8PubMed Central. An unusual presentation of Merkel cell carcinoma: a case report Because the buttocks receive little UV exposure, viral mechanisms may dominate there. There is some evidence that tumors originating outside the head and neck may carry a better prognosis, possibly because the viral mechanism behaves differently than UV-driven carcinogenesis.9JAAD Case Reports. Merkel cell carcinoma originating in the gluteal region
Extramammary Paget’s disease is an intra-epidermal adenocarcinoma that targets apocrine gland-bearing skin, which includes the anogenital and perianal areas.10PubMed. Mammary and extramammary Paget’s disease It often looks like a red, scaly, eczema-like patch, which is why it can be mistaken for dermatitis or a fungal infection for months before anyone thinks to biopsy it. In some cases it signals an underlying internal malignancy, making early diagnosis especially important.11PubMed Central. Extramammary Perianal Paget’s Disease
Dermatofibrosarcoma protuberans is a slow-growing soft tissue sarcoma that can appear virtually anywhere on the body, including the buttocks. A case report described a 26-year-old active duty service member who presented with a firm plaque on her right buttock that had been growing for two years. At a prior visit, the lesion had been dismissed as a scar or rash. When it was finally biopsied, it turned out to be dermatofibrosarcoma protuberans, requiring wide local excision and a repeat surgery when margins came back positive.12Military Medicine. Not Just a Scar: Diagnosing Dermatofibrosarcoma Protuberans in an Active Duty Service Member That two-year delay between first appearance and correct diagnosis is a recurring pattern with buttock lesions.
Metastases That Mimic Primary Skin Cancer
The buttocks can also be a landing site for cancers that started elsewhere in the body. Cutaneous metastases from internal malignancies occasionally present as skin nodules that look like primary skin cancer to the naked eye. A case involving a woman with ovarian cancer who developed pink nodules on her thighs, buttocks, and groin illustrates this well. Under dermoscopy, the lesions showed vascular patterns that mimicked basal cell carcinoma, including serpentine and arborizing vessels.13JAMA Dermatology. Dermoscopic Findings in Cutaneous Metastases Only biopsy confirmed them as metastatic deposits rather than a new skin cancer. For anyone with a history of internal cancer who notices a new skin lesion on the buttocks, this possibility is worth raising with a doctor.
Why Doctors Often Skip the Buttocks
One of the most practical reasons buttock skin cancer is concerning is that it tends to fly under the radar during medical exams. A survey of dermatologists at high-risk skin cancer clinics found that many do not routinely examine the buttocks and genital area during total body skin examinations. The reasons cited were perceived patient discomfort, low prevalence of malignancy in those areas, and the assumption that other specialists would be checking there.14PubMed Central. Total Body Skin Examination Practices: A Survey Study Amongst Dermatologists at High-Risk Skin Cancer Clinics
That creates a gap. The buttocks sit in a surveillance no-man’s-land where dermatologists assume gynecologists or proctologists are looking, while those specialists are focused on their own organs of interest and not performing skin cancer screenings. Meanwhile, you almost certainly are not examining your own buttocks with any regularity, because the logistics of visually inspecting skin you cannot see without a mirror and some contortion are genuinely annoying. The result is that lesions in this area have more time to grow, become misidentified as benign conditions, or get written off as nothing by clinicians who did not look closely.
If you are at a dermatologist for a full-body skin check, it is reasonable to explicitly ask that they include the buttocks, groin, and perianal area. It may feel awkward for a moment, but the alternative is trusting that someone else will look, when often nobody does.
Tanning Beds and Buttock Exposure
Indoor tanning introduces UV radiation to parts of the body that would normally be shielded, and the buttocks are one of them. People who tan nude or in minimal clothing in a tanning bed expose their gluteal skin to UV levels it would never encounter naturally. A large European study involving nearly 146,000 participants found that ever using a sunbed was associated with a higher count of moles and with atypical moles, both of which are melanoma risk markers. Sunbed use was also associated with suspicion of melanoma on screening.15PubMed Central. Association of sunbed use with skin cancer risk factors in Europe: an investigation within the Euromelanoma skin cancer prevention campaign The study did not find a significant association between sunbed use and non-melanoma skin cancer suspicion, but the link with melanoma risk factors is well established enough that indoor tanning represents one of the few ways the buttocks get meaningful UV exposure.
If you used tanning beds extensively and tanned without clothing, your buttock skin has a UV exposure history that is atypical for that body site. This does not mean you will develop cancer, but it shifts your risk profile for that area closer to what your face or forearms would be, which is worth mentioning to a dermatologist.
What to Actually Watch For
Self-examination of the buttocks is not common advice, but the evidence suggests it should be. The challenge is knowing what to look for in an area that is hard to see and where many benign conditions are common. Here is what should prompt a visit to a dermatologist:
- New nodules: A firm, painless lump that was not there before and does not go away after a few weeks. Basal cell carcinoma and Merkel cell carcinoma both present this way.
- Changing moles: A mole that is growing, changing color, has irregular borders, or is asymmetric. The same rules for checking moles on the rest of your body apply here.
- Non-healing sores: Any wound or sore on the buttocks that does not heal within a normal timeframe deserves investigation, especially if you have a history of pressure ulcers or chronic skin conditions in that area.
- Persistent scaly patches: A red, eczema-like patch on the perianal or gluteal skin that does not respond to standard treatments could be extramammary Paget’s disease.
- Firm plaques or scars: A slowly enlarging area of firm or thickened skin, particularly one that was previously dismissed as a scar, could represent dermatofibrosarcoma protuberans or another soft tissue tumor.
A handheld mirror or a phone camera can help you see the area during periodic self-checks. If you have a partner, asking them to take a look periodically is even simpler and gets past the logistical problem entirely.
Immunosuppression as an Amplifier
People whose immune systems are compromised, whether from organ transplant medications, HIV, autoimmune disease treatment, or chemotherapy, face elevated skin cancer risk across the entire body. This applies to the buttocks as much as anywhere else. While the basal cell carcinoma studies found that most buttock cases occurred in patients without obvious immunosuppression, Merkel cell carcinoma patients are disproportionately immunosuppressed. A study of 195 Merkel cell carcinoma patients found that about 8% were profoundly immunosuppressed at diagnosis.16Journal of the American Academy of Dermatology. Clinical characteristics of Merkel cell carcinoma at diagnosis in 195 patients: the AEIOU features For immunosuppressed individuals, regular dermatologic surveillance of the entire body surface, including the buttocks, is especially important because their ability to clear precancerous cells and viral infections is diminished.
Why the “Low UV” Assumption Is Misleading
The reason people doubt that skin cancer occurs on the buttocks is that they equate skin cancer exclusively with sun damage. Ultraviolet radiation is the dominant risk factor for skin cancer in general, but it is not the only one. The buttocks illustrate this clearly: HPV drives some squamous cell and perianal cancers, Merkel cell polyomavirus drives many Merkel cell carcinomas, chronic wound inflammation drives Marjolin’s ulcers, genetic susceptibility operates independently of UV exposure, and extramammary Paget’s disease arises from apocrine gland-bearing skin rather than from UV-damaged cells. Each of these pathways can produce a malignancy on skin that has spent a lifetime under clothing.
Thinking of skin cancer as purely a sun disease leads to two practical mistakes. The first is assuming that covered skin is safe skin, and therefore not checking it. The second is that when a lesion does appear on the buttocks, both patients and clinicians are slower to consider cancer in the differential diagnosis. The dermatofibrosarcoma case where a tumor was dismissed as a scar for two years and the survey showing dermatologists skip the buttocks during skin exams are both consequences of this cognitive bias. Awareness that these cancers can and do develop on the buttocks, even if uncommonly, is the simplest intervention available.