We present a 53-year-old female with a two-year non-healing ulceration of the distal right thumb, initially attributed to a spider bite and barbed wire injury. Despite multiple courses of oral antibiotics and debridement, the ulceration progressed, causing nail loss and requiring several hospital admissions. The chronic nature and resistance to treatment mimicked nail infection, posing a diagnostic challenge.
Upon representing to Emergency Department due to progression of ulceration, dermatology noted subtle pigmentation bordering the wound. Punch biopsies over wound edges revealed an ulcerated and hyperkeratotic epidermis, discohesive groups of pigmented cells in the dermoepidermal junction, and focal pagetoid ascent into the epidermis. Pigmented cells stained positive for SOX10, Melan-A and PRAME, and negative for BRAF and V600E. Breslow thickness was 3.0mm with extensive ulceration (>20mm) and mitosis (5/mm2). Staging PET scans showed diffuse mild FDG uptake at the right thumb and right axillary lymph node. Plastic surgeons performed right thumb amputation with reverse radial forearm flap repair. A right axillary dissection was performed with 1/1 nodes positive, placing the lesion as Stage IIIB subungual melanoma.
The patient commenced monthly adjuvant nivolumab led by medical oncology. Recent CT PET demonstrated no recurrence or metastases. Three-monthly full skin examinations to date revealed no local recurrence, however an added challenge is present due to the flap containing black pigment from the donor site.
This case highlights the importance of excluding melanoma in non-healing ulcers mimicking nail infections, and is a cautionary tale for repairs using tattoo-masked skin for areas requiring further monitoring.