Mast cells in canine mammary gland tumour: number, distribution and EPOR positivity

Association of mast cell density, microvascular density and endothelial area with clinicopathological parameters and prognosis in canine mammary gland carcinomas

Background

Mast cell density has been shown to have both enhancing and inhibiting effects on tumour progression and the ability to predict breast cancer behaviour in humans. However, prognostic results have been contradictory. Some previous studies suggested involvement of mast cells in the progression of canine mammary tumours. This study investigated total, intratumoural and peritumoural mast cell densities by Giemsa staining, and their association with clinicopathological parameters and the disease outcome of canine mammary tumours. In addition, since mast cells promote angiogenesis, the microvascular density and endothelial area were evaluated by CD31 immunostaining.

Results

Intratumoural mast cell density was associated with tumour size, lymph node involvement and tumour-infiltrating lymphocyte count, while peritumoural mast cell density was associated with grade. The endothelial area was associated with grade, mitotic index, tubular formation and proliferation index. Tumours with a high grade, high total intratumoural mast cell density and a larger endothelial area were associated with shorter disease-free survival. Intratumoural mast cell density and grade were found to be independent prognostic factors.

Conclusions

These results suggest that intratumoural mast cell density and the endothelial area can be used to evaluate the aggressiveness of canine mammary carcinomas, while intratumoural mast cell density could be of use as an independent predictor of a prognosis of disease-free survival. Peritumoural mast cell density does not seem to influence tumour behaviour.

Immune Cells and Immunoglobulin Expression in the Mammary Gland Tumors of Dog

Inflammatory cells have a role in tumor progression and have prognostic and therapeutic potential. The immunohistochemical expression for Mast Cell Tryptase, Macrophage Marker, CD79a, IgA, IgM and IgG on 43 cases of canine mammary gland lesions was analyzed. In hyperplasia, a few B cells (BCs) and Tumor-Associated Macrophages (TAMs) were observed, while the number of Tumor-Associated Mast Cells (TAMCs) was the highest. In the peritumoral stroma of malignant lesions, low number of TAMCs and a high number of TAMAs and BCs were present. Immune cells of each type were always lower in the intratumoral than peritumoral stroma. Positivity to CD79a was also detected in the epithelial cells of simple and micropapillay carcinomas. Immunoglobulin reactivity was mainly located in the epithelial cells where an intense positivity to IgA and IgG and a weak positivity for IgM were detectable. On the basis of our preliminary results and literature data, we suggest that such cells and molecules could be directly involved in the biology of canine mammary gland tumors. In breast cancer, stromal inflammatory cells and cancer derived immunoglobulins have been correlated with the progression, malignancy and poor prognosis of the tumor. The results herein reported show that the dog's mammary gland epithelium also expresses immunoglobulins, and they mostly show a direct relationship with the infiltration of macrophages. In addition, this study shows that the infiltration of mast cells, B-cells and macrophages varies depending on the degree of malignancy of neoplasia.

Low Stromal Mast Cell Density in Canine Mammary Gland Tumours Predicts a Poor Prognosis

Tumour histological classification and grade are frequently used to predict the prognosis of canine mammary gland tumours. While these techniques provide some information about tumour behaviour, it is currently difficult to predict which tumours will metastasize. Mast cell density has been shown to predict metastasis in human breast cancer. The present study investigated whether the average mast cell density in 10 high-power (×400) microscopical fields (10 HPFs), evaluated by toluidine blue staining, similarly predicted the behaviour of canine mammary gland tumours. Mast cell density was evaluated in 53 canine mammary neoplasms for which the clinical outcome was known. Stromal mast cell density in malignant tumours that had subsequently developed radiographical evidence of metastasis (n = 21) was significantly lower (P <0.001) than in malignant tumours that did not show evidence of metastases (n = 20) or in benign tumours (n = 12). The density of stromal mast cells that best predicted the disease outcome was ≤10/10 HPFs. Eighty-one percent of malignant tumours with ≤10 stromal mast cells/10 HPFs subsequently metastasized, while only 9.5% of malignant tumours with >10 stromal mast cells/10 HPFs developed metastases. There was a positive correlation between stromal mast cell density and survival time (r_s = 0.50, P <0.001). These findings suggest that assessing stromal mast cell density using toluidine blue staining may represent an easy to perform and cost-effective histopathological measure that, in conjunction with classification and grading, could better predict the behaviour of canine mammary neoplasms.

Tumor⁻Microenvironment Interaction: Analysis of Mast Cell Populations in Normal Tissue and Proliferative Disorders of the Canine Prostate

Mast cells (MCs) are involved in angiogenesis, tissue remodeling and immunomodulation in several human and animal tumors, although their exact role is still controversial. Since no information is available in canine prostate carcinoma (PC) and normal prostate tissues, the aims of this study were to evaluate the possible correlations between MC distribution, molecular expression and microvessel density (MVD) in normal prostatic tissue and proliferative disorders of the canine prostate. All samples (6 normal, 15 benign prostate hyperplasia-BPH, 8 PC) were stained with Toluidine Blue and immunohistochemically evaluated for tryptase, c-Kit (CD117) and CD31. Mast cell density (MCD) and MVD were quantified by the hot-spot method. MCD was significantly increased in periglandular/peritumoral areas, when compared with intraglandular/intratumoral areas, in all groups (p = 0.03). C-Kit expression was strongly associated with PC (ρ = 0.75 p = 0.03), whereas positive correlation between tryptase and c-Kit expression (ρ = 0.64 p = 0.01) was observed in periglandular areas of BPH. MVD showed a correlation with MCD in BPH (ρ = 0.54 p = 0.04). Our data support the importance of c-Kit in regulating MC proliferation. The predominant location of MCs in peritumoral areas of canine PC was similar to the human counterpart, in which PC cells are supposed to produce substances attracting MCs to the tumor microenvironment.