CELLULAR BLUE NEVUS WITH ATYPIA (ATYPICAL CELLULAR BLUE NEVUS) - A CLINICOPATHOLOGICAL STUDY OF 9 CASES

Atypical cellular blue nevus (ACBN) has clinicopathologic features int ermediate between typical cellular blue nevus (CBN) and the rare malig nant blue nevus (MBN)/malignant melanoma (MM) arising in a CBN. Herein we report 9 cases of ACBN. The patients were caucasian (6 females and 3 males) with a mean and median age of 47/51 years. Two patients comp lained of recent changes and about half of these tumors were located o n the buttocks or scalp, averaging 1.5 cm in diameter. Histologically; they were characterized by architectural atypia (infiltrative margin and/or asymmetry) and/or cytologic atypia (hypercellularity, nuclear p leomorphism, hyperchromasia, mitotic figures, and/or necrosis). Assess ment of the expression of 3 tissue markers demonstrated rare solitary cell staining with oncogene product bcl-2, and a proliferative index o f 23+/-19 and 39+/-30 cells/10 high power field with antibodies to PCN A and Mib-1, respectively. No significant differences were detected co mparing the above levels of expression to a control group of 15 CBN; h owever, ACBNs tended to show a higher proliferative index by PCNA and Mib-1 as well as a significantly higher mitotic rate (1/10 HPF vs. 0; p=0.001). Analysis of DNA content showed DNA aneuploidy in both groups . Follow-up data on 9 of 9 patients showed 1 patient dead without dise ase and 8 alive without disease (mean/median follow-up 42/32 months, r ange 15-96 months). No patient during this follow-up time has experien ced either a local recurrence or lymph node or visceral metastasis. Th ese findings highlight the close resemblance of ACBN to the natural hi story of CBN. Nevertheless, many of the distinguishing histologic feat ures of ACBN are also those of MBN. Because of these intermediate clin icopathologic features, ACBN warrant close scrutiny and long-term foll ow-up.