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  • Presentation

How to Determine Whether Melanonychia Warrants Surgical Intervention

Description

The talk explains how to evaluate adult longitudinal melanonychia, especially monodactylous cases, to decide whether surgical biopsy is needed. The first step is distinguishing melanocyte activation from a melanocytic neoplasm: activation is usually benign and can be seen with darker skin types, inflammatory nail disease, or even non-melanocytic tumors, while neoplasms include benign nevi/lentigines and melanoma. A key practical distinction is whether there is nail plate thickening; if so, onychomatricoma is more likely than melanoma, and nail clipping can help confirm it and avoid unnecessary matrix biopsy. Risk stratification relies on features such as band color, Hutchinson sign, and, most importantly, the percentage of the nail plate involved. Grey bands tend to suggest activation, brown bands more often a neoplasm, and involvement of 40% or more of the nail plate is particularly concerning. Hutchinson sign must be distinguished from pseudo-Hutchinson sign, and it can also appear in the lateral nail fold or hyponychium. The speaker also emphasizes that in patients of color, pigmented squamous cell carcinoma is an important alternative diagnosis and may be more common than melanoma. Management depends on risk: low-risk lesions can be monitored, equivocal lesions may undergo tangential shave biopsy, and highly suspicious lesions should have excisional biopsy. If squamous cell carcinoma is suspected, HPV studies can be requested because pathology can be challenging. The lecture ends with a practical overview of tangential shave technique for nail matrix lesions, including reflecting the proximal nail fold, creating a window in the nail plate, shaving the lesion, replacing the nail plate to prevent adhesions, and repairing the fold.

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Conclusions

  • Most longitudinal melanonychia is benign and can often be managed conservatively when clinical and dermoscopic risk is low.
  • The first key distinction is whether the pigmentation is isolated melanonychia or associated with nail thickening, because thickening suggests non-melanoma causes such as onychomatricoma.
  • For melanoma risk stratification, band width is one of the most useful predictors, with involvement of more than about 40% of the nail plate being especially concerning.
  • Other concerning features include broader, darker or brown-to-black bands, variegation, blurred borders, triangular shape, and true Hutchinson sign.
  • A pseudo-Hutchinson sign can mimic melanoma and must be distinguished from true melanocyte extension into the nail fold.
  • In darker skin types, benign melanocytic activation can look more alarming, so clinicians should not overinterpret brown pigmentation or wider bands in isolation.
  • Because nail unit squamous cell carcinoma can present subtly as pigmented longitudinal melanonychia, it should remain in the differential diagnosis, especially when the lesion is lateral or atypical.
  • Low-risk lesions may be monitored, whereas concerning lesions should be biopsied rather than observed.
  • When biopsy is needed but melanoma is not highly suspected, a tangential shave of the nail matrix is a practical tissue-sparing approach.
  • If squamous cell carcinoma is a concern, HPV studies on the specimen may help refine diagnosis and management.
  • Highly suspicious lesions warrant excisional biopsy rather than limited sampling.
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