- -the lunula is part of the matrix and a melanocytic primary lesion implicates lunula involvement
- -slow longitudinal thickening is a characteristic of melanoma (or at least it needs to be ruled out)
Signs that a lesion is not melanocytic
- -arcuate white line associated with redness or pigmentation: in 98% of cases in is traumatic in origin (Hematoma). The ridge can also be felt by pulling back the nail fold
- -proximal clearing: it’s not melanocytic. The proximal nail fold can be pushed back.
- -hemorrhagic dots
- -color that does not extend to the lateral edge.
Dermoscopy is useful but only afford a correct diagnosis in 50% of cases. It all has to do with detecting a regular pattern or an irregular pattern,
- -Regular Pattern: Brown Longitudinal parallel lines with regular spacing and thickness
- -Irregular Pattern: The band compromises multiple longitudinal brown to black lines with irregular spacing and thickness and disruption of parallelism (Braun RP, Baran R, Le Gal FA)
A biopsy is warranted for the following:
- -evolving pigmented streak (3-6 month evaluation period)
- -Heterogenous in pigment in width or length
- -Involvement of proximal nail fold (Hutchinson’s sign)
- -Destruction of Nail
- -Beyond medium darkness (dark)
- -Isolated pigmented band appearing in a 40 to 60 years old
- -Family history of melanoma (controversial)
Make sure that the biopsy is thorough and not just a superficial sample. Getting a report of hyperkeratosis can actually miss the bulk of the lesion and miss the diagnosis.
pigmented longitudinal streaks in children are almost always benign
Excised melanoma is better if possible than amputation. No recurrence is the norm according to breslow thickness (which is the same as anywhere else on the body).
If there is a single digit dystrophy resembling psoriasis or Lichen Planus (LP), it could be amelanotic melanoma or squamous cell carcinoma. Psoriasis or LP tend to affect multiple digits.
Source of Information. CO9. De Berker. Hair and Nail Diseases. 2011 (10) – 20th Annual Congress of the EADV (European Academy of Dermatology and Venerology) – Lisbon (Lisboa), Portugal