Skin cancer screening involves examination of skin for suspicious lesions — moles, growths, sores that might be cancerous. Two main approaches. Self-exam — examine your own skin monthly using mirror or partner help; check all areas including back, scalp, between toes, soles of feet, genitals; look for new lesions or changes in existing ones using ABCDE criteria. Clinician skin exam (CSE) — performed by dermatologist or primary care provider; full-body inspection; dermatoscope (specialized magnifier) used to evaluate suspicious lesions; biopsy any suspicious lesions. Skin cancers screened: basal cell carcinoma (most common; rarely metastasizes; usually curable); squamous cell carcinoma (second most common; can metastasize especially if neglected); melanoma (less common but most deadly; early detection critical). USPSTF 2023 conclusion — insufficient evidence to recommend FOR or AGAINST screening in asymptomatic adults; risk-based approach commonly used. Modestly elevated risk in diabetes, especially for non-melanoma types. Studies suggest: squamous cell carcinoma — about 15-20% increased risk in adults with type 2 diabetes; basal cell carcinoma — about 10% increased risk; melanoma — possibly modest increased risk; less clear. Possible mechanisms: hyperinsulinemia and IGF-1 promoting tumor growth; chronic inflammation; immune dysfunction; oxidative stress; possible direct hyperglycemia effects; some diabetes medications (especially pioglitazone — possible bladder cancer; SGLT2 inhibitors and metformin appear neutral or possibly protective). However, sun exposure remains by far the dominant skin cancer risk factor; diabetes is much smaller contributor. Highest risk individuals: fair skin, history of sunburns, lots of moles, family history of melanoma, immunosuppression, prior skin cancer. Risk reduction: sun protection (SPF 30+ daily, hats, long sleeves), avoid tanning beds, regular self-exams, dermatologist visit if high risk. Diabetes-associated skin conditions warrant monitoring: acanthosis nigricans (dark velvety patches in skin folds — marker of insulin resistance; not cancer); diabetic dermopathy (light brown round/oval scaly patches on shins — common in long-standing diabetes; benign); necrobiosis lipoidica diabeticorum (NLD — yellow-brown patches with raised borders, often on shins; uncommon but classic for diabetes; can ulcerate); diabetic bullae (spontaneous blisters); eruptive xanthomas (from very high triglycerides); skin tags (common with insulin resistance); diabetic ulcers (especially foot ulcers — serious complications). Cancer concerns: NLD lesions can rarely develop squamous cell carcinoma — monitor; chronic non-healing diabetic ulcers can develop squamous cell carcinoma in long-standing cases.
ABCDE Melanoma Warning Signs
| Letter | Sign |
|---|---|
| A | Asymmetry — one half doesn’t match other |
| B | Border irregular, scalloped, or poorly defined |
| C | Color uneven or multiple colors |
| D | Diameter greater than 6 mm |
| E | Evolving — changing in size, shape, color, behavior |
Common Skin Cancers
| Type | Frequency | Behavior |
|---|---|---|
| Basal cell carcinoma | Most common; ~80% skin cancers | Rarely metastasizes; usually curable |
| Squamous cell carcinoma | About 20% of skin cancers | Can metastasize if neglected |
| Melanoma | About 1% of skin cancers | Most deadly; early detection critical |
| Merkel cell carcinoma | Rare | Aggressive; UV and immunosuppression linked |
Diabetes-Related Skin Conditions
- Acanthosis nigricans — insulin resistance marker; not cancer.
- Diabetic dermopathy — shin spots; benign.
- Necrobiosis lipoidica — uncommon; rarely transforms; monitor.
- Diabetic bullae — spontaneous blisters; usually heal.
- Eruptive xanthomas — high triglycerides; resolves with treatment.
- Skin tags — insulin resistance association.
- Diabetic foot ulcers — serious; squamous cell carcinoma risk in chronic ulcers.
- Granuloma annulare — possible diabetes association.
- Yellow skin (carotenemia) — sometimes diabetes-related.
- Vitiligo — autoimmune; more common with type 1 diabetes.
- Fungal infections — more common in poorly controlled diabetes.
Skin Self-Exam Steps
- Stand in front of full-length mirror in well-lit room.
- Examine face, neck, ears, scalp (part hair to look).
- Check chest, abdomen, and front of legs.
- Use hand mirror to check back, buttocks.
- Examine arms (front and back), hands (including between fingers).
- Sit and check tops/bottoms of feet, between toes.
- Check legs front and back.
- Examine genitals and area around them.
- Photograph existing moles to track changes.
- Monthly self-exam recommended for high-risk individuals.
- Have partner help with hard-to-see areas.
Sun Protection
- SPF 30+ broad-spectrum sunscreen daily.
- Reapply every 2 hours and after swimming/sweating.
- Hat (wide-brim preferred).
- UV-blocking sunglasses.
- Long sleeves and pants when feasible.
- UPF-rated clothing for high-sun activities.
- Avoid peak sun hours (10 AM – 4 PM).
- Avoid tanning beds (Class 1 carcinogen).
- Be cautious of reflected UV (sand, water, snow).
- Window UV exposure also accumulates (UVA penetrates glass).
The Bottom Line
Skin cancer screening involves examination of skin for suspicious lesions — moles, growths, sores that might be cancerous. Two main approaches: self-exam (monthly self-check using mirror; check all areas including back, scalp, between toes, soles of feet, genitals; look for new lesions or changes using ABCDE criteria) and clinician skin exam (full-body inspection by dermatologist or primary care provider; dermatoscope used to evaluate suspicious lesions; biopsy any suspicious lesions). Skin cancers screened: basal cell carcinoma (most common — about 80% of skin cancers; rarely metastasizes; usually curable); squamous cell carcinoma (about 20%; can metastasize especially if neglected); melanoma (about 1% but most deadly; early detection critical); rarer types like Merkel cell carcinoma. USPSTF 2023 conclusion — insufficient evidence to recommend FOR or AGAINST routine screening in asymptomatic adults; risk-based approach commonly used. Adults with type 2 diabetes have modestly elevated risk: squamous cell carcinoma about 15-20% increased risk; basal cell carcinoma about 10% increased risk; melanoma possibly modest increased risk (less clear). Possible mechanisms: hyperinsulinemia and IGF-1 promoting tumor growth; chronic inflammation; immune dysfunction; oxidative stress. However, sun exposure remains by far the dominant skin cancer risk factor. Highest risk individuals: fair skin, history of sunburns, lots of moles, family history of melanoma, immunosuppression, prior skin cancer. Diabetes-associated skin conditions warrant monitoring: acanthosis nigricans (insulin resistance marker), diabetic dermopathy (shin spots — benign), necrobiosis lipoidica (uncommon; rarely transforms; monitor), diabetic bullae (spontaneous blisters), eruptive xanthomas (high triglycerides), skin tags (insulin resistance), diabetic ulcers (especially foot ulcers — serious; squamous cell carcinoma risk in chronic ulcers). ABCDE warning signs for moles: Asymmetry, Border irregular, Color uneven, Diameter greater than 6 mm, Evolving (changing). Additional Ugly Duckling sign — mole different from others. Non-melanoma warning signs: new sore that doesn’t heal in 4-6 weeks; persistent rough scaly patch; pearly bump or nodule; recurrent crust or bleeding lesion. Sun protection: SPF 30+ broad-spectrum daily; reapply every 2 hours; hat; sunglasses; long sleeves; avoid peak hours (10 AM – 4 PM); avoid tanning beds (Class 1 carcinogen). When to see dermatologist: any new mole after age 30; changing mole; lesion meeting ABCDE criteria; non-healing sore; concerning skin changes. For adults with diabetes — annual dermatologist visit reasonable for high-risk individuals; vigilant monitoring of diabetes-specific skin conditions; aggressive treatment of any chronic ulcer. See our broader prediabetes detection guide.
