Versican expression in canine carcinomas in benign mixed tumours: is there an association with clinical pathological factors, invasion and overall survival?

Abstract

Background: Components of the extracellular matrix have been studied in an attempt to elucidate the mechanisms involved in the biological behaviour of tumours. The presence of the proteoglycan versican has been strongly associated with cancer development and progression. However, relationship between versican expression and clinical pathological factors and overall survival has not been previously studied in veterinary medicine. Carcinomas in benign mixed tumours (CBMTs) are one of the most common malignant tumours in female canines and can serve as models for studies of tumour progression. The aim of this study was to evaluate the expression of versican in in situ and invasive carcinomatous areas of canine CBMTs and to evaluate possible associations of versican expression with other classic prognostic factors and overall survival.

Results: Clinical staging; histological grade determination; immunohistochemical staining for versican, E-cadherin and Ki-67; and confirmation of invasion areas by staining for p63 and smooth muscle α-actin (α-SMA) were performed on 49 canine cases of CBMT. Tumour invasion was considered when suspicious Haematoxylin-Eosin (HE)-stained areas showed a total loss of α-SMA and p63 immunoreactivity. Versican immunoreactivity was less intense in the areas adjacent to the in situ carcinomatous regions, compared to invasive regions, which showed extensive and strong staining.

Conclusions: Our data reveal that in canine CBMTs, versican expression differs significantly between invasive and in situ areas, suggesting a role for this molecule in tumour progression. Although a direct relationship exists between versican and invasiveness, our results indicate that the isolated evaluation of this proteoglycan does not represent an independent prognostic factor in canine CBMTs.

Figure 1

Carcinoma in benign mixed tumour.A. In situ carcinomatous area with low stromal versican expression. Immunohistochemical stain with Mayer’s haematoxylin counterstain, 40×. B. In situ carcinomatous area with moderate stromal versican expression. Immunohistochemical stain with Mayer’s haematoxylin counterstain, 40×. C. Versican moderate expression adjacent to invasive area. Immunohistochemical stain with Mayer’s haematoxylin counterstain, 40×. D. Versican overexpression adjacent to invasive area. Immunohistochemical stain with Mayer’s haematoxylin counterstain, 40×.

Figure 2

Immunoreactivity for p63, α-SMA, E-cadherin and Ki-67 in in situ and invasive areas. Difference between in situ and invasive areas for p63 and α-SMA (a) and e-cadherin (b) demonstrated by immunohistochemistry. Accumulation of versican in invasive carcinomatous areas when compared to in situ areas (c). *Spearman correlation. §Wilcoxon test.

Figure 3

Carcinoma in benign mixed tumour.A. In situ carcinomatous area in a carcinoma in benign mixed tumour. HE, 60×. B. Evidence of an intact basement membrane. PAS, 60×. C. Integrity of the myoepithelium layer demonstrated by p63 and α-SMA double staining. 60×. D. Microinvasion area in carcinoma in benign mixed tumour (arrow). HE, 60×. E. Discontinuous basement membrane (arrow). PAS, 60×. F. Absence of p63 and α-SMA expression (arrow), 60×.

Figure 4

Carcinoma in benign mixed tumour.A. In situ carcinomatous area with high E-cadherin expression in cell membrane. Immunohistochemical stain with Mayer’s haematoxylin counterstain, 40×. B. Loss of E-cadherin expression in invasive carcinomatous cells. Immunohistochemical stain with Mayer’s haematoxylin counterstain, 40×.

Figure 5

Survival rates of animals with canine mammary carcinomas in benign mixed tumours. Survival curves were estimated with the Kaplan-Meier method followed by the log-rank test. Group 1, represented by cases with low versican expression; and Group 2, represented by cases with versican overexpression.