combined melanocytic nevi
Monday 12 September 2011
Combined melanocytic nevi are composed of 2 or more distinct populations of nevomelanocytes. Most commonly used to describe the combination of blue nevi with common nevi, it may also be applied to other combinations of benign melanocytic proliferations, including Spitz nevi and nevi with deep dermal pigmented nevomelanocytes.
Combined nevi are represented by 4 histologically distinct diagnostic categories:
(1) blue nevus
(2) nevi with deep dermal pigmented nevomelanocytes (plexiform/deep penetrating, inverted type A/clonal)
(3) Spitz or pigmented spindled cell nevus, combined with another type of nevus (usually common or dysplastic)
(4) other combinations including 2 or more nevus types.
Nearly one fifth of these tumors display atypical features; atypia is observed more often in combined nevi with Spitz or deep pigmented elements (26 of 55, 47%, and 25 of 98, 26%, respectively) than in combined common and blue nevi (37 of 336, 11%).