We spontaneously associate the immune system with fighting infections. Yet it plays another, more discreet role: it constantly patrols the skin and eliminates abnormal cells before they become cancers. This is called immune surveillance. When it's lowered, this safety net loosens, and skin-cancer risk climbs. That's precisely why your check-up looks at any immunosuppressant use and the state of your immune defences.
1. The immune system, the skin's unsung guardian
Every day, UV causes errors in the DNA of skin cells. Usually, the immune system spots and eliminates these damaged cells, and keeps in check certain viruses capable of promoting cancers. When defences are weakened, this dual surveillance work diminishes: damaged cells multiply more easily, and skin cancers appear earlier and sometimes more aggressively.
2. Who is concerned?
Lowered immune defences can have several origins. Those particularly concerned include:
- ●Transplant recipients: they take immunosuppressants for life to prevent organ rejection, an indispensable treatment, but one that reduces immune surveillance.
- ●Treated inflammatory or autoimmune diseases: rheumatoid arthritis, inflammatory bowel diseases, psoriasis… when treated with immunosuppressants or biologics.
- ●HIV and certain blood disorders: HIV infection, leukaemias, lymphomas, which weaken the immune system.
- ●More rarely, certain genetic diseases affecting immunity.
3. An excess risk that varies by cancer type
In transplant recipients, skin cancers are the most common cancers, and carcinomas account for about 95% of them. The excess risk doesn't affect all types the same way, however:
| Type of skin cancer | Risk vs general population |
|---|---|
| Squamous cell carcinoma | About × 65 to 100 |
| Basal cell carcinoma | About × 10 |
| Melanoma | Increased (on the order of × 2 to 4) |
| Kaposi's sarcoma (especially with HIV) | Strongly increased |
These cancers appear mainly on uncovered areas (face, neck, hands, forearms), often several at once, and on average 8 to 10 years after a transplant. This explains why monitoring must never be relaxed, but also why, spotted early, these cancers are treated effectively.
4. Why this excess risk?
Three mechanisms combine. First, the drop in immune surveillance lets UV-damaged cells proliferate. Next, certain viruses (notably papillomaviruses) are better tolerated by a body with weakened defences and contribute to skin carcinogenesis. Finally, a few immunosuppressants have their own effect: they disrupt DNA repair or increase sun sensitivity. The common denominator remains the sun: it's the risk factor you can most act on.
5. Reducing the risk: habits that change everything
A large share of these cancers could be avoided by simple lifestyle rules, to adopt for the long term:
- ●Rigorous photoprotection: SPF 50+ sunscreen daily, covering clothes, hat, sunglasses, shade at peak hours and zero tanning beds.
- ●Regular dermatological monitoring: at least once a year, often more depending on the situation, to spot and treat precancerous lesions (actinic keratoses) early.
- ●Attentive self-examination: any new bump, any wound that won't heal or any changing lesion should prompt a prompt consultation.
- ●Dialogue with the medical team: never modify your treatment alone, but report any skin cancer: the doctor can adjust the immunosuppression.
For those concerned, the health check-up is a good starting point to link treatment, immune status and skin monitoring, and to organise suitable follow-up.
Further reading
Related articles on the Iris Prévention blog:
- ●Skin cancer: understanding, spotting and preventing the most common cancer
- ●Skin self-examination: the complete method in 10 minutes
- ●The sun capital: this invisible counter that never recharges
- ●French Society of Dermatology, Dermatological advice for organ transplant recipients
💡 Key tips
- The immune system doesn't only eliminate microbes: it also spots UV-damaged skin cells before they turn cancerous. When it's weakened, this surveillance drops, and skin risk rises.
- In organ-transplant recipients, squamous cell carcinoma risk is multiplied by 65 to 100: it's the most common cancer after a transplant. The good news: caught early, these cancers are treated in the vast majority of cases.
- The sun remains the number-one avoidable trigger. For an immunocompromised person, daily SPF 50+ and covering clothes aren't a summer option but a year-round habit.
- Regular dermatological monitoring (at least once a year, often more) allows precancerous lesions like actinic keratoses to be treated before they evolve. Any bump or wound that won't heal deserves prompt advice.
- Never stop an immunosuppressant on your own initiative. In case of skin cancer, it's the medical team that can adjust the treatment (dose, change of molecule): hence the importance of reporting any diagnosis.
Sources and references
- ●French Society of Dermatology ("Skin and organ transplant" group), Dermatological advice for organ transplant recipients
- ●Traité de Médecine, Skin tumours in the immunocompromised and organ transplant recipient
- ●La Revue du Praticien, Cancer risks after organ transplantation (2024)
- ●The Skin Cancer Foundation, Skin cancers after a transplant
