Most of the time—99 out of 100 cases—skin cancer is clearly visible on the outside of the body (though realising that a funky mole, rash, blemish or lesion is malignant isn't always so easy). Yet there are exceptions to every rule, and this one is no different.

Of course, an advanced melanoma could—depending on its location—cause pain, headaches, or other non-skin symptoms. But by that point you would likely have “a pretty large, ulcerated tumor or wound on the skin,” says Dr Zaineb Makhzoumi. “It’s not something you wouldn’t notice.”

What we're talking about here are the rare exceptions in which non-skin symptoms are your very first clue that you have skin cancer. Here are seven signs you should know about, just in case you happen to fall into that unlucky 1%.