Source:http://linkedlifedata.com/resource/umls/id/C0334448
NCI: A blue nevus characterized by a multinodular cellular infiltrate with a dumb-bell architecture occupying the reticular dermis. The cellular infiltrate often extends into the subcutaneous tissue. The cellular infiltrate is composed of spindle-shaped melanocytes with pale cytoplasm alternating with bundles of pigmented spindle-shaped melanocytes. In occasional cases an increased mitotic activity, focal necrosis, and nuclear pleomorphism may be seen. Such cases with atypical features may have an uncertain malignant potential.