Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android



  • Longitudinal melanonychia (LM) is defined as a longitudinal band of brown-black pigment that runs from the nail matrix to the distal nail plate.

  • It is important to distinguish benign etiologies of LM, like benign melanocytic activation, lentigos and nevi, from nail melanoma.

  • A thorough history, physical exam, and onychoscopic inspection can provide helpful clues and guide management; however, excision and histopathological analysis remains the gold standard for diagnosis.


  • The ABCDEF criteria can help estimate a lesion’s benign nature and guide management.

  • LM in a child is unlikely to be malignant, despite other clinical features.

  • LM that is ≤ 3 mm wide, homogenous in color, and regular in line width and distribution is more likely to be benign.


  • Lesions that are likely benign based on history, physical exam, and onychoscopy may be followed up clinically without biopsy.

  • Whenever there is doubt of whether or not a lesion is benign or a lesion evolves, excise.


  • Lesions affecting multiple digits are more likely to be benign compared to solitary lesions.

  • Any change or lack of resolution of a previously diagnosed benign lesion is reason for re-evaluation.


  • While benign LM is extremely common in individuals with darker phototypes, nail melanoma is still possible in these patients.

  • As solitary lesions in children are likely to be benign, biopsy is typically not necessary and should be avoided.

  • While history, physical exam, and onychoscopy provide helpful clues to guide management, histopathological analysis is the only way to prove a lesion’s etiology.


Onychoscopic evaluation:

  • LM that is a gray homogenous band with a gray background is likely the result of benign melanocytic activation.

  • LM with a brown background, regular width and spacing of lines, and homogenous pigment distribution is likely the result of benign melanocytic proliferation (lentigos and nevi).

  • LM with a brown background, lines of variable width and spacing, and heterogenous pigment distribution is concerning for malignancy in adults.


  • Minimize chronic trauma to the nails by avoiding tight shoes, high heels, and prolonged standing.

  • Educate patients on how to monitor for evolution or change of the lesion (growth, change in color, lack of resolution, etc.).


Melanocytes are a normal constituent cell population of the nail unit. Despite existing in a significantly lower density here than other anatomical skin regions, melanocytes can be found throughout the nail matrix, nail bed, and hyponychium.1,2 Deposition of melanin within the nail plate produces longitudinal melanonychia (LM); this might be due to distal matrix melanocytes activation or hyperplasia.3 Hyperplastic benign pigmented lesions of the nail include nevi and lentigos.

Onychoscopy, or nail dermsocopy, can be used to narrow the differential diagnosis and guide management through distinguishing benign lesions that do not require further follow-up ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.