subungual melanoma

Introduction

melanoma originating under the nail

Etiology

• acral lentiginous melanoma

Epidemiology

• seen in patients with darker skin tones
• 0.7% to 3.5% of all melanoma cases
• 1/3 of all melanoma cases in African Americans, Asians, & native Americans
• peak incidence in 5th to 7th decades of life

Clinical manifestations

• melanonychia of a single nail raises suspicion of subungual melanoma
• pigmentation under the nail extending into the proximal nail fold or other adjacent skin (periungual pigmentation or Hutchinson's sign)
• diameter of 3 mm or more with variegated borders
• a wider diameter of proximal pigmentation than distal pigmentation indicates an expanding lesion
• may also present as diffuse nail discoloration of a single nail

* images

Laboratory

• nail matrix biopsy

Differential diagnosis

• longitudinal melanonychia
  • pigment generally lighter in color
  • pigment diameter constant
  • multiple nails often involved
• subungual hematoma
  • history of trauma
  • pigmentation progresses distally as nail grows out creating a zone of clearing between the proximal nail fold & the pigmentation
  • surrounding skin changes generally resolve within a few weeks

Management

• refer to dermatology

More general terms

• acral lentiginous melanoma
• nail disease