Skin cancer symptoms usually begin as something small and easy to dismiss: a spot that will not heal, a mole that has started to change, a rough pink patch that keeps coming back. Skin is the one organ you can inspect yourself, which is why so many of these cancers are found early and treated simply, and why an unhurried look at your own skin is worth learning to do properly.
In this article you will learn how the three main types of skin cancer behave differently, what the ABCDE letters and the ugly duckling sign mean, why some melanomas hide on palms, soles and under nails, how dermatologists confirm a diagnosis, and what modern treatment looks like. You will also get the honest answer on which blood tests matter here, and which do not.
What skin cancer is, and why the type matters
Skin cancer starts when cells in the epidermis, the outer layer of skin, accumulate enough DNA damage to multiply out of control. According to the Centers for Disease Control and Prevention, too much exposure to UV rays from the sun or from tanning beds causes most skin cancers. One label hides a truth: the main types come from different cells and carry very different risks.
Basal cell carcinoma
The most common cancer in humans. It favors the nose, ears and shoulders, often as a pearly bump with tiny visible vessels, a flat scar-like area, or a sore that bleeds, scabs, heals and reopens in the same place. It grows slowly and almost never spreads elsewhere, but left alone it expands locally and can destroy cartilage, bone or an eyelid. That local damage is the reason to treat it promptly.
Squamous cell carcinoma
This one arises higher in the epidermis and looks scaly, crusted, firm and reddish, sometimes like a wart or an open sore with raised edges, often tender when pressed. It follows years of sun damage and may be preceded by actinic keratoses, the sandpapery patches common on the scalp, ears and backs of the hands. It is highly curable early, though it spreads more readily than basal cell carcinoma, especially on the lip and ear.
Melanoma
Melanoma begins in melanocytes, the cells that make pigment. It accounts for a small share of skin cancers but most of the deaths from them, because it can spread through lymph vessels and blood before it looks dramatic on the surface. A 2025 review in JAMA describes melanoma as the fifth most common cancer in the United States, with most cases still confined to the original site at diagnosis. The commonest form grows sideways within the skin before invading downward, and that phase is the window in which removal is curative. Nodular melanoma skips much of it and looks like a firm raised bump.
Merkel cell carcinoma
Rare but aggressive: a painless, firm, fast-growing, shiny red-to-purple bump, usually on the head, neck or arms of older adults. Because it does not hurt, it is often ignored for weeks. Speed of growth is the clue.
| Type | Typical look | Speed | Tendency to spread |
|---|---|---|---|
| Basal cell carcinoma | Pearly bump, tiny vessels, sore that reopens | Slow, months to years | Very rare; damages tissue locally |
| Squamous cell carcinoma | Scaly red patch, crusted sore, tender lump | Weeks to months | Uncommon, higher on lip and ear |
| Melanoma | New or changing pigmented spot, uneven color | Variable; nodular type is fast | Real, and the reason for early removal |
| Merkel cell carcinoma | Painless firm shiny nodule, red to purple | Fast, weeks | High; needs urgent assessment |
Skin cancer symptoms you can look for on your own skin
Self-examination is useful, and it has a hard limit. It can tell you that a spot deserves professional eyes; it cannot tell you that a spot is harmless. Nothing you see or photograph at home rules cancer in or out; only a pathologist looking at tissue under a microscope can. The goal of a skin check is a short list of spots to show a clinician, not a verdict.
The ABCDE checklist
The ABCDE letters, used by MedlinePlus and by dermatology societies worldwide, are a memory aid for pigmented lesions.
| Letter | What to look at | What raises concern |
|---|---|---|
| A — Asymmetry | Fold the spot in half mentally | The two halves do not match |
| B — Border | The outline | Ragged, notched, blurred or spreading edges |
| C — Color | Shades within one spot | Several browns, black, red, white or blue-gray |
| D — Diameter | Size across | Larger than a pencil eraser, though melanomas can be smaller |
| E — Evolving | Change over weeks or months | New size, shape, color, itch, bleeding or crusting |
Of the five letters, E carries the most weight. A spot that has looked identical for twenty years is far less worrying than one that has changed in the past three months, whatever its size.
The ugly duckling sign
Most people’s moles resemble one another, like siblings. The ugly duckling sign is the observation that a melanoma often stands out from that family: darker, larger, pinker or simply different from the rest. It works where ABCDE struggles, because it compares a spot against your own baseline rather than an abstract rule. In practice, look at one region at a time in good light and ask which spot your eye keeps returning to. Use a mirror or a partner for the back, the scalp, behind the ears and between the toes.
Signs that are not moles at all
Many skin cancers never look like a mole. Watch for a sore unhealed after a month, skin that bleeds from minor contact, a scaly area that returns after every moisturizer, a firm growing nodule, or a new dark streak in a nail. Itchy, symmetrical patches on both elbows or both knees more often reflect a long-standing inflammatory skin condition than a cancer.
The melanomas that get missed
Public health messaging describes melanoma as a dark, irregular mole on sun-exposed skin. That is accurate for the majority and dangerously incomplete for the minority, where late diagnoses concentrate.
Amelanotic melanoma
Some melanomas make little or no pigment. An amelanotic melanoma can look pink, red or skin-colored, and is easily mistaken for a stubborn pimple, a scar, a wart or an insect bite. The 2025 JAMA review counts these among the recognized subtypes, and because ABCDE is built around color, this one slips through it entirely. The clue is persistence: a pink bump that keeps growing, bleeds easily or will not resolve over six to eight weeks deserves assessment regardless of color.
Acral and subungual melanoma
Acral melanoma appears on palms, soles, fingers and toes; subungual melanoma appears in the nail unit. Neither is strongly linked to sun exposure, so sun avoidance offers no protection and a self-check that stops at sun-exposed skin will never find them. In the nail, the early sign is a brown or black band running lengthwise, known as longitudinal melanonychia. Most such bands are harmless, especially in children and in people with naturally more pigmented skin. Concerning features include a single band on one digit, a band wider than a few millimeters, one that is widening or has irregular edges, pigment spreading onto the surrounding skin fold, and nail splitting. A 2023 review of nail unit melanoma notes these tumors are often found late, and that dermoscopy narrows the possibilities but only a biopsy confirms it.
Why detection matters even more in darker skin
Melanoma is less common in people with brown and black skin, but survival is generally worse, and the main reason is stage at diagnosis rather than more aggressive biology. Several factors compound: acral and subungual sites are proportionally more frequent, pigment can mask early color changes, awareness campaigns rarely show darker skin, and neither patients nor clinicians expect the diagnosis. The response is not fear but a habit: check palms, soles, between the toes, the nails and the mouth, and treat a new or changing lesion there as a reason to book an appointment.
What raises the risk of skin cancer, and what lowers it
Ultraviolet exposure, sunburn and tanning beds
Two exposure patterns matter: intermittent intense exposure with blistering sunburns, most strongly tied to melanoma, and cumulative lifetime exposure, which drives basal and squamous cell carcinomas on the face, ears and hands. Sunburns in childhood carry particular weight. Indoor tanning is not safer: tanning devices deliver concentrated ultraviolet radiation, and the CDC counts them alongside sunlight among the main causes of skin cancer. There is no protective base tan; a tan is evidence that DNA damage has already happened. Ultraviolet lamps used to cure gel nail polish have drawn attention too, though a 2024 systematic review found the evidence too thin to quantify any risk.
Personal and family factors
Risk is higher with fair skin that burns easily, red or blond hair, light eyes, many or atypical moles, a previous skin cancer, a first-degree relative with melanoma, or heavy sun exposure at work. People on immunosuppressive drugs after a transplant face a much higher risk of squamous cell carcinoma and need scheduled dermatology follow-up.
Prevention that works
- Seek shade in the middle of the day, when ultraviolet radiation peaks.
- Wear a wide-brimmed hat, sunglasses and tightly woven or UV-rated clothing, which protect more reliably than lotion alone.
- Apply broad-spectrum sunscreen of at least SPF 30 generously, and reapply every two hours.
- Avoid tanning beds and sunlamps entirely, and remember that sand, water and snow reflect ultraviolet radiation back onto you.
- Examine your skin about once a month and keep dated photographs of spots you are watching.
Strict sun avoidance lowers vitamin D production in the skin, worth raising with a clinician. Anyone puzzled by a printout of unfamiliar values can consult a plain-language guide to reference ranges and flags.
How skin cancer is diagnosed
The skin examination and dermoscopy
A clinician examines the whole skin surface, usually with a dermatoscope: a handheld magnifier with polarized light that reveals pigment networks and vessel patterns invisible to the naked eye. In trained hands it improves accuracy and reduces unnecessary removals. Some clinics add total body photography for people with many atypical moles, so change itself triggers biopsy.
Biopsy, and why the type of biopsy matters
A biopsy removes tissue for microscopic examination, and it is the only step that produces a diagnosis. Options include a shave biopsy for superficial lesions, a punch biopsy taking a cylinder of skin through the dermis, and an excisional biopsy removing the whole lesion. When melanoma is suspected, excision is preferred, because measuring how deep the tumor has grown requires its full depth in the specimen.
Breslow thickness and staging
For melanoma, the most influential number is the Breslow thickness, the depth of the tumor in millimeters measured from the skin surface. Thinner tumors carry a better outlook and need smaller margins. The report also notes ulceration, mitotic rate, margins and subtype. A 2023 review in The Lancet summarizes the standard approach: primary melanoma is treated with wide excision, and the margin is set by tumor thickness. When a melanoma is thick enough, the surgeon may offer a sentinel lymph node biopsy, in which a tracer identifies the first lymph node draining that area of skin so it can be examined. A clear node refines staging; an involved node changes the treatment plan.
Screening: who benefits, and who does not
Population-wide screening differs from checking a worrying spot. In 2023 the United States Preventive Services Task Force concluded that current evidence is insufficient to weigh the benefits and harms of routine visual skin examination by a clinician in adolescents and adults with no signs or symptoms. That is a statement about missing evidence, not proof that screening fails, and it excludes two groups: anyone with a symptom is being evaluated rather than screened, and high-risk patients follow a dermatologist’s own schedule.
Treatment options for skin cancer
Surgery and local treatments
Most skin cancers are cured surgically. Standard excision removes the tumor with a margin of normal-looking skin. Mohs micrographic surgery removes tissue in thin layers, each checked under the microscope until no cancer cells remain at the edge; it spares the most healthy tissue and is often chosen on the face, ears and hands. Topical fluorouracil or imiquimod creams, cryotherapy and photodynamic therapy treat actinic keratoses and superficial basal cell carcinomas. Radiotherapy is an option when surgery is unsuitable.
Advanced melanoma: immunotherapy and targeted therapy
The outlook in advanced melanoma has changed substantially over the past decade. Checkpoint inhibitors release a brake on the immune system so it can recognize tumor cells; they are standard for melanoma that has spread and, in selected cases, after surgery to reduce recurrence. Targeted therapy is used when the tumor carries a BRAF mutation, found by testing tumor tissue. Immunotherapy has reshaped several solid tumors, and readers making comparisons often read the lung cancer overview or the breast cancer guide. Because these drugs loosen immune restraint, they can also inflame healthy organs: most often the thyroid, skin, bowel and liver, less often the pituitary and adrenal glands.
Where blood tests fit in skin cancer care
Here is the honest framing, often misrepresented online. No blood test screens for skin cancer, and none diagnoses it. A suspicious lesion is assessed by examination, dermoscopy and biopsy, and a normal set of blood results says nothing about the spot on your shoulder.
Blood work has two genuine roles once a diagnosis exists. The first is staging in advanced melanoma, where teams sometimes measure lactate dehydrogenase levels in the blood, an enzyme released when cells are damaged anywhere in the body. It is not specific to melanoma and rises with exercise, infection and muscle injury, but in stage IV disease it carries prognostic weight and forms part of formal staging. It plays no part in detecting early skin cancer.
The second role is monitoring during systemic treatment. Before and during checkpoint immunotherapy, teams commonly repeat a thyroid-stimulating hormone measurement, since the thyroid is most often affected. They watch the liver enzyme alanine aminotransferase for immune-related hepatitis, track a fasting blood glucose value because new-onset diabetes is an uncommon but recognized effect, and check a morning cortisol level to assess the pituitary and adrenal axis. Most protocols also repeat a complete blood count panel each cycle. Catching these shifts early lets a team act before symptoms appear.
When to see a doctor
Book an appointment, rather than waiting, if any of the following applies.
- A sore, scab or ulcer has not healed within four to six weeks.
- A mole is changing in size, shape, color or texture, or has started to itch, bleed or crust.
- One spot clearly stands out from all your other moles.
- A pink, red or skin-colored bump keeps growing or bleeds from light contact.
- A new dark band has appeared in a nail, particularly a single band on one digit or one that is widening.
- A new or changing spot has appeared on a palm, a sole, between the toes or inside the mouth.
- A firm nodule has grown noticeably within a few weeks.
- You have had a skin cancer before, or you take immune-suppressing medicines.
Bring dated photographs if you have them, and describe the timeline in weeks. A short, specific history helps a dermatologist more than any home measurement.
Latest scientific advances
Artificial intelligence reads dermoscopic images well, but it is not a diagnosis
A 2025 meta-analysis, a study that pools results from many earlier studies, examined artificial intelligence systems that classify dermoscopic images. Across dozens of tests they separated melanoma from non-melanoma with high accuracy on the image sets they were given. What this means for you: the technology is promising as an assistant for clinicians, but a phone app cannot clear your mole. Most systems were tested on curated images rather than snapshots of real skin, and everyday performance still needs confirmation.
Treating before surgery, not only after, in node-positive melanoma
A large randomized trial published in 2024 compared two strategies in stage III melanoma, meaning melanoma that has reached nearby lymph nodes but no further. One group had two cycles of combined immunotherapy before surgery; the other had surgery first, then a year of immunotherapy. Going first led to markedly fewer recurrences in the first year, and most of those patients had much or all of the tumor destroyed by the time of surgery. What this means for you: the sequence of treatment is now a fair question for the oncology team, though follow-up is still accumulating.
Immunotherapy after surgery keeps working years later
A seven-year analysis published in 2024 followed people with stage III melanoma given either a year of immunotherapy after surgery or a placebo. Around half of those treated were still free of recurrence at seven years, against roughly a third of those who were not. What this means for you: adjuvant treatment, meaning treatment after surgery to lower the chance of the cancer returning, brings a durable benefit rather than a delay. It still has to be balanced against side effects, which is why blood monitoring matters.
Glossary
| Term | Definition |
|---|---|
| Actinic keratosis | A rough, scaly patch caused by years of sun exposure. A small proportion can progress to squamous cell carcinoma, so these patches are often treated. |
| Amelanotic | Describes a melanoma that produces little or no pigment, so it looks pink, red or skin-colored instead of brown or black. |
| Breslow thickness | The depth of a melanoma in millimeters, measured under the microscope from the skin surface. It strongly influences surgical margins and outlook. |
| Checkpoint inhibitor | A drug that releases a natural brake on immune cells so they can attack tumor cells. Used in advanced melanoma and Merkel cell carcinoma. |
| Dermoscopy | Examination of the skin with a handheld magnifier and polarized light, which reveals color and vessel patterns invisible to the naked eye. |
| Melanocyte | The skin cell that produces melanin, the pigment giving skin its color. Melanoma arises from these cells. |
| Mohs micrographic surgery | A technique that removes a tumor in thin layers, checking each layer under the microscope during the operation to spare healthy tissue. |
| Sentinel lymph node biopsy | Removal and examination of the first lymph node draining the tumor area, used to refine melanoma staging. |
| Subungual | Located under the nail. Subungual melanoma often begins as a dark band running lengthwise along the nail. |
| Ugly duckling sign | The observation that a suspicious lesion tends to look different from a person’s other moles, which usually resemble one another. |
Frequently asked questions
Is skin cancer curable when it is caught early?
In most cases, yes. Basal cell carcinoma and squamous cell carcinoma found early are usually cured by a single outpatient procedure, and thin melanoma removed with adequate margins has a very good outlook. The picture is different once melanoma has spread beyond the skin, although treatment for advanced disease has improved considerably in recent years. Because outcomes hinge so heavily on how early a lesion is removed, the useful action is not reassurance-seeking online but an appointment for anything new, changing or persistent.
Can skin cancer cause symptoms beyond the skin?
Early skin cancer generally causes no symptoms other than the lesion itself. If melanoma spreads, symptoms depend on where it goes and might include a swollen lymph node, unexplained weight loss, persistent fatigue, a cough that will not settle, headaches or bone pain. These have many far more common causes and are not a way to detect skin cancer. They are a reason to see a doctor, who will look at the whole picture rather than a single sign.
How often should I examine my own skin at home?
About once a month suits most adults, and more often if a dermatologist has advised it. Do it in good light after a shower, work through the body region by region, and use a mirror or a partner for the back, scalp and backs of the legs. Include the palms, soles, between the toes, the nails and the mouth. Photographs with a date and a ruler in frame make change much easier to judge later.
Can a smartphone app tell me whether a mole is cancerous?
No. Some apps and artificial intelligence tools perform well on high-quality dermoscopic images in research settings, and the technology may become a useful triage aid. In everyday conditions, with variable lighting, focus and skin tones, their reliability is not established, and a reassuring result can delay a needed appointment. Treat any app as a prompt to get checked, never as permission to skip it. Diagnosis requires a clinician and, ultimately, a biopsy.
Do people with darker skin need sun protection?
Yes. More melanin offers some natural protection against ultraviolet damage, but it is partial, sunburn is still possible and skin cancer still occurs. Melanoma in people with brown and black skin is more likely to appear on palms, soles and nail beds, sites where sun protection is irrelevant and self-examination is the only defense. Because these cancers are more often found late, outcomes are generally worse, which makes routine checks of these areas particularly worthwhile.
Does a mole I have had for years still need checking?
A stable mole that has looked the same for many years is reassuring, and most melanomas actually arise on previously normal skin rather than within an existing mole. That said, an old mole that starts to change, itch, bleed, thicken or shift color does need review. The relevant question is not how long a spot has been there, but whether anything about it has altered recently.
Sources
- Centers for Disease Control and Prevention — Skin Cancer Basics, 2024 — cdc.gov
- MedlinePlus, National Library of Medicine — Skin Cancer, 2024 — medlineplus.gov
- US Preventive Services Task Force — Skin Cancer: Screening, 2023 — uspreventiveservicestaskforce.org
- Joshi UM, Kashani-Sabet M, Kirkwood JM — Cutaneous Melanoma: A Review — JAMA, 2025 — doi.org/10.1001/jama.2025.13074
- Long GV, Swetter SM, Menzies AM, et al. — Cutaneous melanoma — The Lancet, 2023 — doi.org/10.1016/S0140-6736(23)00821-8
- Ertürk Zararsız G, Yerlitaş Taştan SI, Çelik Gürbulak E, et al. — Diagnosis of melanoma with artificial intelligence systems: a meta-analysis and systematic review — Journal of the European Academy of Dermatology and Venereology, 2025 — doi.org/10.1111/jdv.20781
- Blank CU, Lucas MW, Scolyer RA, et al. — Neoadjuvant Nivolumab and Ipilimumab in Resectable Stage III Melanoma — New England Journal of Medicine, 2024 — doi.org/10.1056/NEJMoa2402604
- Eggermont AM, Kicinski M, Blank CU, et al. — Seven-year analysis of adjuvant pembrolizumab versus placebo in stage III melanoma, EORTC1325 / KEYNOTE-054 — European Journal of Cancer, 2024 — doi.org/10.1016/j.ejca.2024.114327
- Conway J, Bellet JS, Rubin AI, et al. — Adult and Pediatric Nail Unit Melanoma: Epidemiology, Diagnosis, and Treatment — Cells, 2023 — doi.org/10.3390/cells12060964
- Metko D, Mehta S, McMullen E, et al. — A systematic review of the risk of cutaneous malignancy associated with ultraviolet nail lamps — European Journal of Dermatology, 2024 — doi.org/10.1684/ejd.2024.4616
Further reading
- Colorectal cancer: symptoms, causes and treatments
- Prostate cancer: symptoms, causes and treatments
- Ovarian cancer: symptoms, causes and treatments
- Liver cancer: symptoms, causes and treatments
- The patient’s guide to AI lab interpretation
Understand your lab results with BloodSense
Skin cancer is diagnosed on the skin, not in a tube of blood, yet laboratory results still surround the journey: the thyroid, liver, glucose and cortisol values followed during immunotherapy, the enzyme lactate dehydrogenase used in advanced melanoma staging, and the routine blood counts repeated at every treatment cycle. BloodSense reads those reports with you, explaining what each marker measures, how far a value sits from its reference range, and which questions are worth raising at your next visit. It helps you understand your results; it does not diagnose, and it does not replace your doctor or your dermatologist.
