Fibrillar pattern of a plantar acquired melanocytic naevus: correspondence between epiluminescence microscopy and transverse section histology.

The main epiluminescence microscopy (ELM) patterns observed on volar acquired melanocytic naevi are the parallel-furrow, the lattice-like and the fibrillar patterns. Because of the peculiar arrangement and configuration of epidermal rete ridges in the glabrous skin, the traditional histological picture does not provide an exact correlation with ELM features. In particular, the fibrillar pattern lacks a histopathological correlate. To clarify the microscopic features of the fibrillar pattern, we used transverse histological sectioning to study an acquired compound melanocytic naevus of the sole, characterized by a mixed parallel-furrow/fibrillar pattern on ELM. Low-magnification images of transverse sections allowed us to highlight the typical anatomical arrangement of the volar skin clearly, while high-magnification images demonstrated that the fibrillar pattern corresponded to parallel striae of intensely pigmented corneocytes arranged obliquely to the cutaneous surface.