Most of these were published prior to advanced imaging techniques and in an are where the link between supernumerary digits and associated malformations was not well known to pediatricians. Despite these limitations, it appears that bilateral supernumerary digits are only rarely associated with systemic malformations. Acral lesions to be considered in the clinical differential of supernumerary digits include verruca, acquired digital fibrokeratoma, multinucleate cell angiohistiocytoma, acral angiofibroma, and neurofibroma. One important distinction is that each of these lesions is usually acquired. In addition, with the exception of the acquired digital fibrokeratoma, most of these entities are multiple.
Further distinction is possible based upon characteristic anatomic predilections.
Acral angiofibroma occurs in periungal sites and acquired digital fibrokeratoma is typically found on the digits proper, frequently near a joint. Neurofibromas uncommonly occur on the digits, and when present, are soft and often pedunculated. The most important histologic mimics are neurofibroma and traumatic neuroma. Although both have similar histologic features, neurofibromas are characterized by diffuse loosely arranged bundles of spindle cells intimately associated with wiry strands of collagen and mucoid material. Traumatic neuromas are typified by discrete collections of haphazardly arranged nerve fascicles, with accompanying Schwann cells, and perineurum.