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Could this pigmented toenail lesion be a melanoma?

Registrar Dr Oliver Starr decribes how he didn’t want to risk missing his first melanoma

 

The patient

This sporty 29-year-old man was a rare attender at the practice. He came to see me about a painless pigmented lesion under his left little toe nail that he thought had been there about two months. He remembered bashing the adjacent toe on a bed frame but was adamant he had not knocked his little toe.

He was expecting it to grow out, but when it seemed to be moving down into the nail bed he became concerned. His girlfriend's mother had been treated for malignant melanoma and she encouraged him to get advice.

First instinct

Purely on the balance of probabilities I thought this was a simple collection of blood. But even on pushing down the cuticle I could not see a clearing of the pigment distal to the skin. It also seemed to have variable pigmentation and an irregular shape. I didn't want to miss my first diagnosis of melanoma.

Differential diagnosis

• Subungual haematoma

• Junctional naevus

• Skin malignancy

• Infection of the nail or nail bed

To the naked eye all these differentials look similar under a nail. I would have expected a haematoma to be growing out after two months, but he thought it was progressing proximally. The patient said it was better to ‘get it out' even if it was benign. A senior partner at my practice agreed, so I referred him to the plastic surgeons.

Getting on the right track

Under a local anaesthetic ring block, the nail was removed. The operation note recorded that the lesion was attached to the underside of the nail, not the nail bed itself. Histology revealed numerous fungal spores typical of candida with a mild haemorrhagic reaction and fibrinous exudates. The patient breathed a sigh of relief, as did I. Although in retrospect we had made an inappropriate two-week referral, we managed to rule out malignancy and get the right diagnosis quickly. We used topical clotrimazole to cover any residual infection on the toes.

Dr Oliver Starr is a GP registrar in Hitchin, Hertfordshire

Toenail lesion

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