What should you know about melanoma under a toenail?

A dark mark under a toenail can also follow an injury, pressure from footwear, a fungal infection or another benign cause. Features that deserve examination include a band that widens or changes colour, pigment extending onto the surrounding skin, bleeding, a persistent sore, or a nail becoming distorted without a clear injury. A photograph with a ruler beside the toe can help show change over time, but it cannot replace an examination.

A clinician may inspect every nail and the skin around it with magnification. If the appearance is concerning, a biopsy can examine the nail unit. Do not scrape, burn or repeatedly cover the mark before assessment.

Book a dermatology appointment for a new or changing toenail mark, especially when it affects one nail and does not grow out with the nail. Bring a list of medicines and mention previous injuries, fungal treatment and any personal or family history of melanoma. If testing confirms melanoma, the team may discuss surgical excision and additional staging, including a sentinel lymph node biopsy in selected cases.

Seek prompt review for pain with swelling, recurrent bleeding, pus, a rapidly enlarging area, or a nail that separates from its bed. These signs can reflect infection, trauma or a tumour and need direct assessment. Go to urgent care for fever with spreading redness, severe pain, or feeling acutely unwell.

Could this involve the nail unit rather than the nail plate alone? Do I need a biopsy, and what will it involve? If melanoma is confirmed, how will you assess its depth and spread? How should I protect and monitor the toe during healing?