The causes of nail apparatus pigmentation presenting to a melanoma screening clinic a prospective study

Advanced stage primary cutaneous malignant melanoma (PCMM) has a high mortality. PCMM may affect any area of the skin, including the nail apparatus (malignant melanoma or subungual melanoma). Although nail apparatus malignant melanoma (NAMM) is rare, delayed diagnosis carries a poor prognosis.

The primary aim was to study the range of nail presentations and identify key patterns to aid in differential diagnosis. A secondary aim was to quantify the number of patients requiring surgery, indications for biopsy, and the incidence and characteristics of NAMM.

This was a prospective study of all referrals with nail apparatus pigmentation to a weekly dedicated melanoma screening clinic over a 6-month period.

In total, 2246 patients were included. Of the 38 patients referred with nail pigmentation, 1 (2.6%) was diagnosed with NAMM and involved a fungating amelanotic lesion of the right hallux. The remaining patients were diagnosed with subungual haematoma (20/38; 52.6%), viral wart (2/38; 5.4%), acral fibrokeratoma (1/38; 2.6%), myxoid cyst (3/38; 7.9%), fungal nail infection (4/38; 10.5%), Pseudomonas nail infection (1/38; 2.6%), benign linear pigmentation (2/38, 5.3%), Bowen disease (1/38, 2.6%), psoriatic nail changes (2/38; 5.3%) and matrix malalignment (1/38; 2.6%). Of the eight patients (21.1%) who required surgery, five had a biopsy taken and three underwent surgery. Only 14 cases were followed up by Dermatology. NAMM accounted for 0.7% of all melanomas diagnosed.

We illustrate the wide range of diagnoses for pigmented nail presentations and highlight the late presentation of advanced disease in a patient presenting with NAMM.