Myxome des gaines nerveuses de l'hyponychium

This type of tumour is characteristic of nerve sheath myxoma, and is almost certainly of Schwannian origin, although distinct from Schwannoma. It is rare, occurs after the age of 35 years and is preferentially located in the extremities of the limbs. There has only been one other description of its occurrence under the fingernail, in which it was described as neurothekeoma. However, neurothekeoma is entirely different, being more cellular, with no expression of protein S100, and marked by the NKIC3 antibody; it occurs in children or young adults, and is frequently found on the face. These two tumours were confused for some time, but today they must be completely distinguished from one another. These myxomas must be completely excised because of the risk of relapse. Finally, they should be distinguished from other myxoid tumours of the digits, certain of which can be malignant.