A frequent cause of concern for podiatrists (and sometimes their patients) are brown marks under the toenail. Melanoma or Haematoma? Sometimes it’s reassuring to get some help with these sorts of cases.
One of the great things about the internet is the range of free videos, articles and presentations. The problem is – how do you know the information is credible? Well, for this blog I just want to promote an excellent resource produced by one of the best educators in dermoscopy in the UK today – Dr Stephen Hayes. Dr Hayes is a former GP with a long interest in dermatology who since 2012 has been an Associate Specialist in Dermatology at University Southampton Hospitals. Much of his time is dedicated to screening patients referred to the hospital with pigmented lesions.
Dr Hayes produces a regular blog on dermoscopy which is straight forward and provides a great learning resource for those with an interest in this area. For this article, Dr Hayes has kindly agreed to share cases from his blog (dermoscopy.blogspot.com).
Case:
Figure 1: Brown marks under the nail
Melanoma skin cancer may appear under a finger or toenail, but it is uncommon. The main signs to look out for are a dark brown or black line down the length of the nail which slowly gets wider from the base, pigment spreading out into the skin next to the nail (Hutchinson’s sign) a lump, and destruction of the nail. These are all ‘red flag’ warning signs requiring urgent specialised medical attention. The 2 images (figure 1 & 2) are of a typical case of a black mark under a toenail for several weeks. there was no recollection of trauma. The patient had gone online and worried themselves sick that they had a melanoma.
Figure 2: Same image as in Figure 1 (under the dermatoscope)
It’s blood. Study the deep blue globules, this is what blood looks like under the nail. It grows out slowly. This could not possibly be a melanoma as there is a clear gap between the pigment and the proximal nail fold (the base of the nail). There are no melanocytes in the skin underneath the nail plate, if a melanoma is there it has to have grown in from outside. Blood under the nail can result from the most minimal trauma. The blood grows out very slowly. I have it on the authority of two top nail experts, Dr David de Berker of Bristol, and Professor Luc Thomas of Lyon, France, that if you can see a gap between the pigment and the proximal nail fold, it can’t be a melanoma.
Its always good to remember to remember that most brown marks under the nail are haematoma and rarely melanoma, although there are red flags to look out for, as Dr Hayes points out. A brown longitudinal band (on a single nail) which is widening, has different shades of pigment within it, or has spread onto the cuticle (Hutchinson's sign) are signs that warrant immediate referral. It’s also good to remember that patients with darker skin types may develop multiple brown lines in multiple nails which commonly occurs naturally with ageing.
Keen eyed readers will recall the image on this sites home page which demonstrates an extensive melanoma of the nail unit. This lesion has spread and eventually destroyed the nail unit resulting in nail plate destruction. Unexplained single nail plate destruction is also something that warrants careful investigation even in the absence of brown pigment.
Figure 3: Nail Unit Melanoma which has spread onto the skin
(Hutchinson's Sign)
If a patient has a “new” area of brown pigment emerging from under the cuticle and moving distally, of course, a haematoma will clear the proximal nail fold leaving a gap. If you are not sure, re-book a patient to return and you should observe a gap appearing as the bruise grows out. Here is an image from Dr Hayes, demonstrating just that:
Figure 4: A haematoma growing out from the proximal nail fold
In previous article, I also talked about patients who used their phones camera to take a selfie of their toe to demonstrate just the same (click here).
Dr Hayes Blog Article Links:
Article on spotting melanoma on the foot and in the nail: