Nail plate dermoscopy
Introduction
Examination of the nail plate free edge permits the observation of subungual localized hyperkeratosis in epithelial tumors of the nail matrix such as Bowen disease, squamous cell carcinoma, onychopapilloma, onychomatricoma and seborrheic keratosis. In onychomatricoma, its remarkable “dotted” free edge surface constitutes another criterion in favor of this diagnosis. In onychopapilloma, the sharp “spine-shaped” hyperkeratotic plug visible underneath the nail plate in the area of nail changes is also very helpful.
It is also of interest to dermoscopically examine the distal free edge of the nail plate in cases of melanonychia striata[1] since the position of the pigment in the nail plate gives an interesting indication of the location of the pigmented lesion with the matrix (i.e. proximal versus distal matrix). Since the dorsal aspect of the nail plate is derived from the proximal matrix, the presence of the pigment in the upper part of the nail plate free edge will indicate the site of the causal lesion in the proximal part of the matrix. In contrast, the presence of pigment in the lower part of the nail plate will favor a distal matrix location of the causative lesion. Knowing or estimating the location of a pigmented lesion preoperatively is of tremendous importance in order to inform the patient of the possible esthetic consequences of the biopsy. A biopsy taken from the distal matrix will create a nail plate with an almost invisible defect from underneath whereas a biopsy of the proximal matrix will cause a visible defect of the nail plate surface[2].
Nail plate free edge examination
Examination of the nail plate free edge permits the observation of subungual localized hyperkeratosis in epithelial tumors of the nail matrix such as Bowen disease, squamous cell carcinoma, onychopapilloma, onychomatricoma and seborrheic keratosis. In onychomatricoma, its remarkable “dotted” free edge surface constitutes another criterion in favor of this diagnosis. In onychopapilloma, the sharp “spine-shaped” hyperkeratotic plug visible underneath the nail plate in the area of nail changes is also very helpful.
It is also of interest to dermoscopically examine the distal free edge of the nail plate in cases of melanonychia striata[3] since the position of the pigment in the nail plate gives an interesting indication of the location of the pigmented lesion with the matrix (i.e. proximal versus distal matrix). Since the dorsal aspect of the nail plate is derived from the proximal matrix, the presence of the pigment in the upper part of the nail plate free edge will indicate the site of the causal lesion in the proximal part of the matrix. In contrast, the presence of pigment in the lower part of the nail plate will favor a distal matrix location of the causative lesion. Knowing or estimating the location of a pigmented lesion preoperatively is of tremendous importance in order to inform the patient of the possible esthetic consequences of the biopsy. A biopsy taken from the distal matrix will create a nail plate with an almost invisible defect from underneath whereas a biopsy of the proximal matrix will cause a visible defect of the nail plate surface[4].
Digital dermoscopy follow-up
On skin, dermoscopy has been proven efficient (level of proof “A”) to accurately distinguish melanoma from other pigmented lesions but its sensitivity does not reach 100%. For this reason, digital follow-up of high-risk patients and of flat doubtful lesions has been developed. By sequential dermoscopic imaging of the lesion(s) and comparison of images over time, it permits determination of minor changes in shape, color or architecture of a given lesion, to allow an even earlier diagnosis of melanoma than would be possible with classic dermoscopy. Many publications have validated the concept of sequential dermoscopic imaging of cutaneous lesions in order to make a more accurate and precise diagnosis of melanoma (level of proof “B”)[5] but even though the situation appears to be similar for nails, the value of digital sequential imaging of doubtful cases of melanonychia striata has not been yet evaluated in published prospective studies. However, we have some experience with sequential dermoscopy and believe that, in selected indications, digital follow-up of nail pigmentation could help to demonstrate changes over time and therefore aid the diagnosis of suspected melanoma in patients in whom both clinical and dermoscopic criteria are at first insufficient to permit its positive diagnosis. Since the concept has not been established in large series, we will just briefly mention this technique here. However, it is our opinion that prospective large studies are definitively needed to better establish the role and impact of digital dermoscopy follow-up of nail pigmentation.
- ↑ 28 Braun RP, Baran R, Saurat JH, Thomas L. (2006) Surgical Pearl: dermoscopy of the free edge of the nail to determine the level of nail plate pigmentation and the location of its probable origin in the proximal or distal nail matrix. J Am Acad Dermatol 55(3): 512–13.
- ↑ 29 Jellinek N. (2007) Nail matrix biopsy of longitudinal melanonychia: diagnostic algorithm including the matrix shave biopsy. J Am Acad Dermatol 56(5): 803–10.
- ↑ Braun RP, Baran R, Saurat JH, Thomas L. (2006) Surgical Pearl: dermoscopy of the free edge of the nail to determine the level of nail plate pigmentation and the location of its probable origin in the proximal or distal nail matrix. J Am Acad Dermatol 55(3): 512–13.
- ↑ Jellinek N. (2007) Nail matrix biopsy of longitudinal melanonychia: diagnostic algorithm including the matrix shave biopsy. J Am Acad Dermatol 56(5): 803–10.
- ↑ Altamura D, Avramidis M, Menzies SW. (2008) Assessment of the optimal interval for and sensitivity of short-term sequential digital dermoscopy monitoring for the diagnosis of melanoma. Arch Dermatol 144(4): 502–6.
