The relation of nervous elements to intradermal nevi. As electron microscopic study.

Intratumoral nerves of dermal nevi were investigated by electron microscopy in order to elucidate the role of neural elements in the development of these tumors. The following results were obtained: 1. Intratumoral nerves exhibit an increased cellularity, but the number of myelinated fibers is reduced. 2. Nevus cells type B and C are frequently present within nerve fascicles. 3. Unmyelinated axons were found in close relationship to nevus cells. 4. Schwann cells may show proliferations similar to early stages of neurofibroma and can be differentiated from unpigmented tumor cells by their relation to axons only. These findings indicate that identical cell populations are present within the intratumoral nerves and the tumor itself. Therefore, the theory of a neural component in the histogenesis of intradermal nevi is supported.