Missed opportunity to diagnose subungual melanoma: potential pitfalls!

Subungual melanoma, an uncommon form of acral melanoma that arises within the nail matrix, accounts for 1%-3% of all cutaneous melanoma in Caucasians. As subungual melanoma presents in a more disguised manner than cutaneous lesions, increased vigilance is required. It most commonly presents as a discolouration of the nail, nail splitting or nail-bed bleeding. Black pigmentation of the adjacent nail fold, termed Hutchinson's sign, may be a diagnostic clue. Treatment of subungual melanoma remains surgical with wide local excision and amputation primary modalities. We present the case of a 61-year-old man with an 18-month history of a left thumb nail-bed abnormality and a 6-week history of left axillary lymphadenopathy. One year earlier, he presented to the emergency department with a purulent discharge from his left thumb but declined nail-bed ablation. He was referred to the 'Hand and Plastic Injuries Clinic' by his general practitioner and diagnosed with a chronic traumatic-induced nail-bed injury. As his symptoms did not improve, he was referred to the 2-week wait Skin Cancer Clinic. The left thumb nail-bed was excised as a nail unit down to bone, and the diagnosis of melanoma was rendered. Left axillary lymphadenopathy was confirmed as metastatic melanoma. He underwent amputation of his left thumb at the interproximal phalangeal joint, and a left axillary node dissection was performed. No residual melanoma was identified in his thumb. Microscopically, his left axillary dissection confirmed 9 out of 36 positive nodes for metastatic melanoma with extracapsular spread. He was staged at IIIC disease. This case report demonstrates missed opportunities to diagnose subungual melanoma and acts as a cautionary tale in considering this pathology in the differential diagnosis of nail-bed lesions with prompt referral for further investigation.