A Pigmented Thumbnail Lesion
Am Fam Physician. 2018 Sep 15;98(6):377-378.
An 82-year-old man who worked in a hardware store presented for a routine health examination. He did not have fevers, chills, night sweats, or unintentional weight loss, and his vital signs were normal. His only concern was a nontender lesion on his thumbnail that he noticed about three months earlier. He had no recent trauma.
Physical examination revealed a longitudinal melanonychia on the radial edge of the left thumbnail. Brown-black pigmentation was noted over the proximal nail fold (Figure 1). The pigment tapered distally, and a V-shaped nick in the nail plate was present at the distal aspect of the streak.
Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?
A. Acral melanoma.
B. Melanonychia striata.
C. Nail matrix hematoma.
D. Pseudomonas aeruginosa infection.
E. Subungual verruca vulgaris.
The answer is A: acral melanoma. Recognition of a subungual melanoma can be challenging, and prognosis is generally worse than for other cutaneous melanomas because of delayed diagnosis.1,2 Hutchinson nail sign (black or brown pigmentation extending from the nail bed to the proximal or lateral nail folds) is associated with acral lentiginous melanoma.3 More common benign causes of longitudinal melanonychia, such as matrix nevi, may look similar but typically occur concurrently in multiple nail beds.4 Biopsy of the lesion is warranted to rule out melanoma. In situ nail matrix melanomas may be treated with conservative excision of the entire nail apparatus (nail plate, bed, and matrix).5
Melanonychia striata is a band of black or brown pigmentation due to melanin beneath the nail plate and is common in patients with darker skin complexions. The band is of uniform width, whereas melanoma of the nail apparatus is generally wider at the base, tapering distally, and may cause knicking of the distal
Referencesshow all references
1. Metzger S, Ellwanger U, Stroebel W, Schiebel U, Rassner G, Fierlbeck G. Extent and consequences of physician delay in the diagnosis of acral melanoma. Melanoma Res. 1998;8(2):181–186....
2. Cohen Busam KJ, Patel A, Brady MS. Subungual melanoma: management considerations. Am J Surg. 2008;195(2):244–248.
3. Kopf AW. Subtle clues to diagnosis by gross pathology. Hutchinson's sign of subungual malignant melanoma. Am J Dermatopathol. 1981;3(2):201–202.
4. Levit EK, Kagen MH, Scher RK, Grossman M, Altman E. The ABC rule for clinical detection of subungual melanoma. J Am Acad Dermatol. 2000;42(2 pt 1):269–274.
5. Braun RP, Baran R, Le Gal FA, et al. Diagnosis and management of nail pigmentations. J Am Acad Dermatol. 2007;56(5):835–847.
6. Lipner SR, Scher RK. Evaluation of nail lines: color and shape hold clues. Cleve Clin J Med. 2016;83(5):385–391.
This series is coordinated by John E. Delzell Jr., MD, MSPH, Associate Medical Editor.
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