Design: Population-based cohort with linked registry and death data, 1990–2019
Population: 21,503 first kidney transplant recipients in Australia and New Zealand
Primary outcome: Skin cancer mortality relative to the general population
Effect: SMR 11.1 overall; 4.5 melanoma; 34.5 keratinocyte cancer

This study linked 21,503 first kidney transplant recipients from the Australia and New Zealand Dialysis and Transplant Registry with national death registers from 1990 to 2019, over 212,317 person-years.

There were 251 skin cancer deaths: 82 from melanoma and 169 from keratinocyte cancer. Compared with the general population, skin cancer mortality was 11.1 times higher overall, 4.5 times higher for melanoma and 34.5 times higher for keratinocyte cancer. The excess appeared in both sexes, at every age, in every region and in every decade, and was greatest in the highest-ultraviolet regions such as Queensland (SMR 14.8).

The striking figure is the keratinocyte one: cancers usually thought of as low-mortality become a leading cause of skin cancer death under long-term immunosuppression. Australia and New Zealand have unusually high ultraviolet exposure, so absolute rates will differ elsewhere, but the relative excess is the reason transplant patients need a dermatology pathway rather than ad hoc referral. Indian data on transplant skin cancer are limited, and darker skin types carry lower baseline risk, but the immunosuppression effect is the same.

Arrange regular full skin examinations for kidney transplant recipients, with intervals set by skin type and history.
Fast-track any new or changing lesion in a transplant patient rather than placing it on a routine list.
Treat squamous cell carcinoma in a transplant recipient as a potentially lethal cancer, not a minor excision.
Teach sun protection and self-examination at transplant and repeat it at follow-up.
Discuss with the transplant team whether immunosuppression can be adjusted after repeated skin cancers.

Why it matters

Keratinocyte cancers that rarely kill in the general population become a real cause of death after transplant.

The statistics, in plain English

A standardised mortality ratio of 11.1 means transplant recipients died of skin cancer about 11 times as often as people of the same age and sex in the general population. The keratinocyte figure of 34.5 is large partly because such deaths are rare in the general population, so the comparison number is small.