[Superficial acral fibromyxoma in a sub-matricial location: An unusual variant]

Superficial acral fibromyxoma (SAFM) is a benign soft tissue tumor located in the acral areas, particularly the peri- and sub-ungueal areas. Sub-matricial localisations have not been reported to date.

We report herein the clinical and pathological presentation of three cases of SAFM located solely under the matrix. The patients presented with pseudo-clubbing, onychogryphosis or triangular macrolunula. The histopathological appearance was characteristic.

SAFM is a slow-growing, skin-colored, firm nodule, located chiefly on the digits or the toes, and especially in the nail area. It may or may not be painful. Microscopically, it presents as a relatively well-circumscribed but unencapsulated dermal tumor, composed of spindle shaped cells integrated in a myxocollagenic matrix, sometimes invading the subcutis. Tumor cells diffusely express CD34. A conservative surgical approach is recommended. Both clinicians and pathologists should be aware of this entity in order to avoid misdiagnosis, which can lead to unwarranted mutilating surgery.

Sub-matricial localisation of SAFM is extremely rare and may present as pseudo-clubbing, isolated onychogryphosis or a triangular macrolunula. A conservative surgical approach should be recommended.