Sunshine might stop certain cancers from growing, including skin cancers, according to two new studies.
The findings do not mean sun protection advice should be ignored
One found it helped beat the deadly skin cancer malignant melanoma. The other found the sun helped with non-Hodgkin lymphoma.
It could be down to the vitamin D made by sun-exposed skin, the Journal of the National Cancer Institute reported.
Experts warned too much sun could cause cancer and advised people to protect themselves against sun damage.
The lymphoma study, by Swedish researchers at the Karolinska Institute and Uppsala University together with scientists from Denmark, found UV rays from the sun and sun lamps reduced the risks of developing cancer by 30-40%.
They based their findings on interviews with more than 3,000 lymphoma patients and 3,000 healthy members of the public.
Meanwhile, researchers at the University of New Mexico in Albuquerque looked at the influence of sun exposure on the risk of dying from malignant melanoma.
They found melanoma patients with higher levels of sun exposure were less likely to die than fellow melanoma patients.
Previous studies have hinted that skin cells damaged by the sun commit suicide, thereby cutting the risk of cancer.
Alternatively, it might be the increased production of vitamin D which reduces cancer risk, said the authors.
Be sun 'savvy'
Cancer Research UK experts said it was also possible that patients who already had melanoma and a lot of sun exposure were prone to less aggressive tumour type.
CRUK's Dr Julia Newton Bishop said: "We should view with caution the assertion that sunlight may be beneficial for melanoma overall.
"There is no doubt that sun exposure causes melanoma in the first place.
"Therefore, the public health message should remain unchanged.
"It's important to remember that covering up during the peak hours of sunshine, seeking shade and wearing factor 15 plus sunscreen, as advised in Cancer Research UK's SunSmart campaign, are still the best ways to avoid sunburn that can lead to skin cancer."
In an accompanying editorial, Dr William Blot from the International Epidemiology Institute in Rockville, the US, said further studies of sunlight and vitamin D's connection to cancer were warranted.