Although not always the case, symptoms of cancer typically affect the area of the body in which the disease is growing. This can lead to some more obvious signs, such as lung cancer causing a cough and bowel cancer leading to blood in the toilet.
However, it can also result in some more unusual symptoms that you might not always pick up on.
One such sign can appear in the fingernails, according to an expert.
Responding to a video on TikTok, NHS surgeon Doctor Karan Rajan, warned people to look out for a dark vertical streak on the nail.
This can be caused by an aggressive type of skin cancer, he said.
In the original post the creator shared an image of their own dark streak on the nail.
They captioned the video: “Me: Having this for 10 years, thinking it was a cool streak in my nail…It’s cancer.”
Replying, Dr Rajan – who is better known online as Dr Raj – revealed to his more than five million followers that he also has dark pigmentation under his nail, although benign.
He explained: “Now I’ve got this dark vertical streak on the nail of my ring finger. This is known as melanonychia.
“And it’s actually pretty common in people with darker skin.
“There can be lots of causes for a dark line on your nail from infection, medication side effects, trauma, blood clots, and one particular cause is a rare type of skin cancer called a melanoma or in this case a subungual melanoma.”
Dr Raj urged people to seek medical help if they notice this sign, or any other changes on the skin.
He added: “Although this particular subtype of melanoma is quite rare, it happens in about one percent of all melanoma cases, as with any skin lesions, if you notice a rapid change in size, colour or shape go check it out.
According to the Cleveland Clinic subungual melanoma differs from other skin cancers in that it isn’t linked to sun exposure.
It is “most likely” to develop in your big toe, thumb or index finger.
The clinic warns: “Many people assume discoloured nails are from stubbing their toe or infection.
“Nail melanoma is often discovered later than other cancers because people don’t know the warning signs. Learning how to spot nail melanoma can help you get treatment as soon as possible.
“When subungual melanoma is caught early (before the cancer spreads), it’s more likely to have a successful outcome.”
A line caused by subungual melanoma is usually less than three millimetres wide but can grow over time.
Other warning signs of subungual melanoma include if your nails:
- Split, crack or deform in some way
- Have an irregular pigment (the discoloration isn’t even)
- Swell or be inflamed
- Lift away from your nail bed
- Develop an ulcer, nodule or start to bleed
- Discolour the skin surrounding the nail (Hutchinson sign).
If you experience any of these symptoms you should speak to your GP.