The proliferative activity of four malignant
cellular blue nevi (MCBN) was assessed in routinely fixed,
paraffin-embedded material using staining for the argyrophilic nucleolar organizer regions (
AgNORs), immunohistochemical staining for
proliferating cell nuclear antigen (
PCNA [PC10]), and
DNA flow cytometry. The objective was to determine whether the evaluation of proliferative activity could represent a useful diagnostic parameter. Four
cellular blue nevi (CBN), 10
melanocytic nevi (MN), four common
blue nevi (BN), and 10 conventional
malignant melanomas (MMs) were selected as controls. In the MCBN the mean AgNOR number, evaluated on the basis of 100
tumor cells, was 8.33 +/- 0.83; NORs were small and dispersed throughout the nucleus; the mean
PCNA score was 31.93% +/- 4.4; and two of the cases were
aneuploid and two diploid. In the CBN the AgNOR count was 3.69 +/- 0.56; NORs were large and mainly grouped in a central cluster; the mean
PCNA score was 3.53% +/- 1.28; and three of the cases were diploid and one
aneuploid. The AgNOR counts in the MCBN were significantly different from those in the CBN (P = .0002), MN (3.04; P = .00001), and BN (2.93; P = .00006), whereas they were not significantly different from those in the conventional MMs (7.64; P = .58). The
PCNA (PC10) scores in the MCBN were significantly different from those in the CBN (P = .00003), MN (2.05%; P = .00001), and BN (5.06%; P = .00002), whereas they were not significantly different from those in the conventional MMs (28.9%; P = .49). In all the cases a linear relationship between AgNOR counts and
PCNA scores was observed (r = .94, P = .00001). Our results indicate that AgNOR analysis and
PCNA immunostaining can be regarded as useful additional parameters for the diagnosis of MCBN.