Cellular blue nevus. An ultrastructural study.

Cellular blue nevus can be clinically and histogenetically confused with malignant melanoma but remains a benign neoplasm of uncertain histogenesis. This paper reports the ultrastructural features of three cases of cellular blue nevus and emphasizes melanosomal alterations, including immature and granular forms, multiple layers of basement membrane around vessels, nerve fibers and tumor cells; endothelial fenestrations and banded structures within the nerve and outside in the stroma. A unifying concept of neural crest derived tumors is presented to better understand the histogenesis of cellular blue nevus.