EN
Fifteen specimens of the canine mammary gland tumors were examined for the expression of the mRNA c-myc gene by in situ hybridization with the use of a v-myc probe. The expression of c-myc mRNA was observed in fourteen cases of adenocarcinoma. There was no hybridization signal in one case of adenoma. A correlation between the size and the rate of the tumour growth and the hybridization pattern was found. Five solid, rapidly growing adenocarcinomas showed very strong hybridization with the v-myc probe. Six tubular adenocarcinomas without the tendency to enlarge were characterized by scattered foci of strong hybridization with the v-myc probe. A moderate hybridization signal was observed in three large but slowly increasing in size, part solid, part tubular adenocarcinomas.