Overexpression of HER-2/neu in Malignant Mammary Tumors; Translation of Clinicopathological Features from Dog to Human

Background: Canine mammary gland tumors (CMGTs) are the most common tumor found in bitches. Changesin HER-2/neu genes in human breast cancer (HBC) lead to decrease in disease-free survival (DFS) and overallsurvival rate (OSR). Previous studies have demonstrated that the biological behavior of malignant mammarygland tumors (MMGTs) is similar to that of HBC. The present study aimed at evaluating the relationship betweenoverexpression of HER-2/neu and clinicopathological features in MMGTs to represent a model of prognostic factorsfor HBC. Materials and
Method: The clinicopathological data of 35 MMGTs were obtained. Immunohistochemicalstaining with HER-2, Ki-67 and CD34 markers was conducted with sections from paraffin-embedded blocks.According to standard protocols, histological type, grade, margin status, lymphovascular invasion (LVI), HER-2/neu score, proliferation rate and microvessel density (MVD) of tumors were determined and the association ofHER-2/neu overexpression with these parameters was assessed statistically.
Results: The IHC results showedthat 12 (34.3%) cases were HER-2/neu positive. Statistical analyses indicated a significant relationship betweenHER-2 positivity and tumor grade (p=0.043), which also was demonstrated with cancer stage (p=0.035), tumormargin involvement (p=0.016), proliferation index (p=0.001) and MVD (p=0.001); however, there was no statisticalrelationship between LVI and tumor size. Overexpression of the HER-2/neu gene in MMGTs results in similarbiological behavior as that of HBC; as a result, these tumors have can be considered to have important similaritiesin clinicopathological characteristics.
Conclusions: MMGTs can be regarded as an HBC animal model. Furtherstudies in this field would result in new treatments that could be beneficial for both dogs and humans.