Definition and Categorization of Combined Melanocytic Nevi.
Johanna L Baran, Lyn M Duncan. Massachusetts General Hospital, Boston
Background: “Combined nevus” is a term used to describe tumors composed of two or more distinct populations of melanocytes. While this term has historically been used to describe the combination of blue nevi with common nevi, it has more recently been applied to other combinations of benign melanocytic proliferations. We sought to document the use of this terminology and the incidence and distribution of these tumors to propose consistent diagnostic nomenclature for practical use and comparison.
Design: The electronic records were reviewed for all cases that included both the terms "combined" and "nevus" in the diagnosis field between the years 2000-2010. The cases identified were then examined for diagnosis, presence of atypia, as well as age and sex of the patient.
Results: 514 combined nevi were identified, represented by four histologically distinct diagnostic categories: “common” junctional, dermal, compound or dysplastic nevus combined with 1) blue nevus, 2) Spitz or pigmented spindled cell nevus, 3) deep pigmented nevus (plexiform, deep penetrating, inverted type A), or 4) other combinations with or without a common nevus component. Of these nevi, 18% displayed cytological atypia, observed more often in combined common nevi with Spitz or deep pigmented elements (26/55, 47% and 23/97, 24% respectively) than in combined common and blue nevi (37/337, 11%). There was no difference in age distribution or gender between histological categories or in the banal versus atypical nevi.
|Diagnosis||All cases||Inside cases||Consult cases||Age (mean)||Sex|
|Combined common and blue||337||321||16||4-86 (47)||179F:158M|
|Combined common and Spitz||55||50||5||7-76 (35)||34F:21M|
|Combined common and deep pigmented||97||84||13||4-79 (40)||58F:33M|