[Histology of the pigmented granular rankenneuroma (author's transl)].

We report on a case of a 40 years old female patient with a lentil-sized tumor of the left pinna present since early childhood. Histologic examination revealed pigmented granular "rankenneuroma". The lesion is unencapsulated but fairly well marginated in the dermis. It is composed of varying numbers of spindle-shaped or polyhedral cells arranged in intertwining and parallel bands separated by strands of collagen. The fascicles follow the preexisting nerve truncs. All layers of the dermis may be involved, but only rarely is the superficial subcutaneous tissue invaded. The fascicles of the tumor are generally constructed in a similar fashion. In the center one see argyrophile granular alterated unpigmented cells- Those elements are surrounded by mostly bipolar cells containing varying amounts of melanin. Silverstaining shows transition from spindle-shaped cells to granular degenerated elements. It is thought that the tumor most likely originates from the proliferation of the granular degenerated Schwann cells. The characteristic feature of tumor parenchyme is the association of the granular Schwann cells with cutaneous melanoblasts.