"Compound blue nevus": a reappraisal of "superficial blue nevus with prominent intraepidermal dendritic melanocytes" with emphasis on dermoscopic and histopathologic features.

Abstract

We describe 5 cases of "compound blue nevus" (CBN) ("superficial blue nevus with prominent intraepidermal dendritic melanocytes," "Kamino nevus"). Dermoscopically in 2 of 4 cases the bluish pigmentation characteristic of blue nevi was centrally replaced by a black lamella, with black dots and brown globules also observed in one case, thus revealing a structural asymmetry suggestive of melanoma. Histopathologically, pigmented parakeratosis was the underlying histopathologic finding of black lamella and dots/globules. Immunohistochemistry highlighted the unique histopathologic feature of CBN, namely, single dendritic melanocytes at the dermoepidermal junction with striking intraepidermal prolongations. Our findings confirm that CBN is a distinctive variant of blue nevus that may mimic cutaneous melanoma both clinically and dermoscopically.