Olympic gold medallist Mack Horton thanks fan who noticed cancerous mole on his chest

The Australian swimmer has since undergone surgery to have the melanoma removed

Horton had the dark mole on his upper torso removed after advice from an anonymous fan (Getty)

Olympic champion Mack Horton has thanked an anonymous spectator who potentially saved his life by noticing an abnormal mole on his chest.

The Australian swimmer, who won gold in the 400m freestyle at this summer’s Rio Olympics, has since undergone surgery to have the melanoma removed.

Horton revealed that the alarm was raised by someone who had watched the swimmer on television and subsequently contacted Australia’s Olympic swimming team.

“Shout out to the person that emailed the swim team doctor and told me to get my mole checked out. Good call. Very good call,” Horton wrote in a message on Instagram.

The picture accompanying the message showed Horton giving the thumbs up to the camera while wearing a bandage on his chest.

Images of Horton over the course of his career show the mole growing larger and turning darker; two common signs that a previously benign mole has become malignant.

Australia has one of the highest incidence and mortality rates of skin cancer in the world, at two to three times the levels in the UK, the US and Canada.

According to Cancer Council Australia, skin cancers account for around 80 per cent of all newly diagnosed cancers in the country.

Horton provoked controversy during this summer’s Games after he called the previous 400m Olympic champion, China’s Sun Yang, a “drug cheat”.

Sun subsequently accused Horton of deliberately attempting to psych him out, and the Australian’s social media channels were inundated with messages from the Chinese swimmer’s supporters.