Common Blue Nevus

Abstract

The “common” blue nevus (also called nevus of Jadassohn- Tiéche or dendritic blue nevus) is a benign neoplasm composed of dendritic melanocytes accompanied by numerous melanophages and by variable degrees of fi brosis. The lesion is entirely contained in the dermis, without a junctional component. The common blue nevus constitutes a clinical and morphological continuum with the so-called “cellular” blue nevus, discussed in the next chapter. The dichotomy, common versus cellular, is entrenched in the literature but ignores the great variety of appearances that blue nevi have. Despite this morphological diversity, blue nevi are a more genomically homogeneous group than other types of nevus. Almost all of them have mutations in one of two related genes, gna-q and gna-11. Their morphological features are also linked by histopathologic patterns suggesting derivation from perineural precursor cells and migration through the dermis, as occurs with congenital nevi, and smaller so-called congenital pattern nevi.