Renaut bodies. Benign disease process mimicking neurotropic tumor infiltration.

BACKGROUND: Mohs micrographic surgery maximizes the potential for complete tumor removal with normal tissue preservation through the histologic examination of all tissue margins. One component of the histologic examination is the evaluation of excised nerves for the presence of tumor infiltration. During such an evaluation, a subperineurial structure was noted. OBSERVATION: Further investigation displayed a discrete, loosely textured, cell-sparse, whorled, subperineurial structure that invaginated into the peripheral nerve. Inflammation was absent and the nuclei were monomorphous. These findings are those seen with Renaut bodies.
CONCLUSIONS: Renaut bodies are found at sites of nerve compression. Mechanical factors are thought to play a major role in pathogenesis. Cells comprising the Renaut body are fibroblasts of perineurial origin with the extracellular matrix comprised of collagen fibrils, basal lamina material, and oxytalan filaments. Renaut bodies are important insofar as the surgeon must recognize that they are benign. Histologic characteristics that differentiate Renaut bodies from malignant neurotropic infiltration are: (a) a cell-sparse mass, (b) absence of nuclear atypia, (c) less than expected inflammatory infiltrate, and (d) well-defined borders.