Nucleolus-organizing regions (AgNORs) are silver-stained loops of DNA
transcribing to ribosomal RNA. Quantitative analysis helps to differen
tiate normal tissue from malignant tissue and can be used for diagnosi
s in several kinds of tumours. The analysis of AgNORs can also be used
in dermatopathology for diagnostic and prognostic purposes. Apart fro
m skin tumours such as basal,cell carcinomas and squamous cell carcino
mas, this technique is of interest principally for melanocytic lesions
. Benign naevi can be distinguished from malignant melanomas by simple
counting of the AgNOR dots. For the differentiation of dysplastic nae
vi, Spitz naevi and malignant melanomas, this parameter alone is not s
ufficient. By combination of several AgNOR parameters (number, size, p
attern of dispersal) only, significant differentiation could be achiev
ed. The prognostic value of AgNORs remains to be examined.