PROLIFERATIVE ACTIVITIES IN SPITZ NEVUS COMPARED WITH MELANOCYTIC NEVUS AND MALIGNANT-MELANOMA USING EXPRESSION OF PCNA CYCLIN AND MITOTIC RATE

Proliferative activity in Spitz nevus (SN) was determined using prolif erating cell nuclear antigen (PCNA) immunostaining and by assessing th e mitotic rate. It was compared with that in compound melanocytic nevu s (MN) and in malignant melanoma (MM). The PCNA index (number of posit ive cells/1,000 tumor cells) in SN was 72.8 +/- 45.5% (mean +/- SD), w hich was statistically significantly higher than that in MN (7.2 +/- 2 .7%) and lower than that in MM (248.5 +/- 110%). The PCNA-positive cel ls in SN and MM were found both in dermal and junctional nests, while those in MN were found almost exclusively in the dermal nests. The mit otic rate in SN was 1.4 +/- 0.96%, while it was nothing in MN and 5.4 +/- 4.2% in MM. There was a statistically significant correlation betw een the PCNA index and the mitotic rate at r = 0.8946, p < 0.001. The PCNA index, however, appeared to show the proliferative activity of SN more clearly than did the mitotic rate.