In this skin cancer update video, Associate Professor Giuseppe Argenziano discusses a study by the International Dermoscopy Society that sheds light on melanoma under the fingernail. He explains the causes of nail pigmentation and what criteria are used for diagnosing such irregularities as melanoma.
Pigmented nails can be caused by a haemorrhage, drug use, an ethnic predisposition, a nevus, or a melanoma. The discolouration usually appears as a band of dark blue or black underneath the fingernail. Before this study was conducted in 2002, ‘regular’ bands on the nail were typically associated with nevi while ‘irregular’ bands symptomised melanoma. However, some early melanomas can appear regular – a symptom usually associated with nevi. More specific criteria were therefore needed to differentiate between the various causes of pigmented nails.
A/Prof Giuseppe Argenziano coordinated the study that sought to establish such criteria. Its key finding was that – while the regularity of the pigmented nail band is very important – the size of the band is the critical factor in determining the difference between a nevus and a melanoma. In other words, the researchers found that the regularity of a band was not the only criterion for distinguishing nevi from melanoma, but ought to be considered in conjunction with the band’s size.
The study found that a small band that covers less than one third of the nail is considered unlikely to be a melanoma, and can be monitored with follow-up checks. However, a pigmented band that covers more than a third of the nail is considered highly suspicious and ought to be acted upon accordingly.
A/Prof Giuseppe Argenziano remarks that melanomas might be dismissed as nevi in cases where they appear regular, if the additional size criterion is not conjunctly considered.
