Clefts in intradermal nevi: an ultrastructural study

Six intradermal melanocytic nevi, two with and four without intercellular slitlike spaces, were examined by light microscopy and electron microscopy of deparaffinized tissue. The spaces were partially lined by elongated nevus cells and contained a few collagen fibrils. Other features in both groups included an abundance of (1) immature elastic tissue comprised of aggregates of microfibrils lacking an amorphous component and (2) collagen fibrils that were finer than in normal dermis and did not form compact bundles. We propose that these elastic tissue and collagen fiber changes diminish the resistance of the dermis to the mechanical stress of the biopsy procedure and histologic processing, resulting in the formation of artifactual clefts.