Subungual Melanomas

  • Subungual melanomas:
    • Are rare subtypes of melanoma:
      • Accounting for 0.7% to 3.5% of all reported cases
      • The hallux and thumb are the most commonly affected sites
    • Antecedent trauma:
      • Has been reported in 25% to 55% of patients
    • Diagnosis is often delayed because of:
      • Inadequate biopsies
      • Lesion neglect
      • Confusion with benign melanonychia, hematoma, chronic trauma, or fungal nail infection (onychomycosis)
  • The classic features suggestive of melanoma include:
    • Melanotic lesions arising from the nail matrix and longitudinal melanonychia:
      • Defined as a band of pigmentation extending from the proximal nail fold / lunula throughout the nail to the free edge
      • Any band greater than 3 mm in width or associated with discoloration of the lateral or proximal nail folds (Hutchinson’s sign):
        • Mandates biopsy of the nail matrix and bed with either incisional or punch techniques:
          • Partial or total avulsion of the nail plate is usually needed to perform biopsy
  • Management of these lesions requires sound oncologic resection with consideration of functional deficits:
    • Margin principles in melanoma are maintained:
      • Which means amputation is often necessary
    • Special consideration is given to the hallux and thumb:
      • As the complete loss of either can cause substantial disability
    • For the hallux amputation of the digit preserves the metatarsal head, and for the thumb, efforts are made to preserve bone proximal to the interphalangeal joint, if appropriate margins allow:
      • Excision of the nail bed, matrix, and proximal nail fold will not provide adequate margins
  • Mohs micrographic surgery has been used in several small series for selected cases of melanoma-in-situ only, and this technique would not provide adequate resection of this melanoma deeper melanomas
  • Amputation of the thumb just proximal to the interphalangeal joint is the best approach:
    • As it provides for adequate margins while preserving a stump for some functional use. Radical amputation would also provide adequate margins, but the functional deficit created is unnecessary
  • References:
    • Ross MI. Excision of primary melanoma. In: Balch CM, Houghton AN, Sober AJ, Soong S-J, eds. Cutaneous Melanoma. 5th ed. St. Louis: Quality Medical Publishing; 2009:251-274.
    • Sureda N, Phan A, Poulalhon N, Balme B, Dalle S, Thomas L. Conservative surgical management of subungal (matrix derived) melanoma: report of seven cases and literature review. Br J Dermatol. 2011;165:852-858.
    • Tan KB, Moncrieff M, Thompson JF, et al. Subungual melanoma: a study of 124 cases highlighting features of early lesions, potential pitfalls in diagnosis, and guidelines for histologic reporting. Am J Surg Pathol. 2007;31:1902-1912.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s