Introduction

Mammary tumors are the most frequent neoplastic processes in bitches. Evaluating overall survival of dogs with mammary tumor becomes difficult due to a large variation of the development of these injuries. (Peleteiro 1994) Adequate anatomopathological diagnosis is of great importance to determine the patient's prognosis and adequate treatment (Misdorp et al. 1999). The aim of this study is to report the frequency of mammary gland diagnosis of the Laboratory of Comparative Pathology, Department of General Pathology, Institute of Biological Science, Federal University of Minas Gerais, Brazil between January 2000 and July 2008.

Materials and Methods

The material evaluated in this study was originated from Veterinary Teaching Hospital and Laboratory of Comparative Pathology of the Federal University of Minas Gerais, Brazil. 1552 samples were examined from January 2000 to July 2008. The following aspects were analyzed: animal gender, part of the tissue analyzed and characteristics of the injury. In all cases involving mammary gland, the injury was categorized according its histological type (Misdorp et al. 1999).

Results

From a total of 1552 biopsies, 1479 cases (95.5%) were from the canine gender, 45 cases (3%) from the feline gender and in 28 cases (1.5%) the gender was not specified. Of all cases evaluated 1078 (69%) were mammary injuries that were divided in 423 (39.5%) benign processes and 655 (60.5%) malignant processes. From the 45 cases of the feline gender, 26 (57.77%) were mammary injuries. The frequency of the 2 (7.69%) benign mammary injuries was: 1 (50%) fibrocystic alterations and 1 (50%) mastitis. The frequency of the 24 (92.30%) main malignant injuries was: 2 (8.33%) carcinoma in mixed tumor, 1 (4.16%) in situ carcinoma in mixed tumor, 1 (4.16%) papillary carcinoma, 4 (16.66%) carcinoma with no other specification, 8 (33.33%) carcinoma tubular and 8 (33.33%) other tumors. From the 28 cases in which gender was not specified, 12 (42.85%) were mammary injuries. The frequency of the 3 (25%) benign mammary injuries was not specified was: 2 (66.66%) benign mixed tumor and 1 (33.33%) epidermoid cyst. The frequency of the 9 (75%) main malignant injuries of cases in which gender was not specified was: 6 (66.66%) carcinoma in mixed tumor, 1 (11.11%) in situ carcinoma in mixed tumor and 2 (22.22%) papillary carcinoma. From the 1479 cases of the canine gender, 1040 (70.31%) were mammary injuries. The frequency of the 418 (40.19%) benign mammary injuries was: 209 (50%) benign mixed tumor, 44 (10.52%) adenoma, 42 (10.04%) papilloma, 30 (7.17%) fibrocystic alterations, 74 (17.70%) others and 19 (4.54%) did not have considerable alterations. The frequency of the 622 (59.80%) main malignant injuries of the canine gender was: 264 (42.44%) carcinoma in mixed tumor, 75 (12.05%) in situ carcinoma in mixed tumor, 67 (10.77%) papillary carcinoma, 63 (10.12%) carcinoma with no other specification, 46 (7.39%) carcinoma tubular and 107 (17.02%) others.

Discussion and Conclusions

This study demonstrated that the mammary mixed tumor was the most common neoplastic process and that the distribution of malignant tumors was superior to benign tumors. These results are similar to ones described in the literature, reinforcing the importance of clinical aspects and anatomopathological exams to obtain knowledge on the evolution of mammary gland tumors (Peleteiro 1994, Sorenmo 2003). The biological behavior of some canine neoplasias, such as mixed tumors, strengthens this necessity. Mixed benign tumors are the most frequent mammary neoplasias in the female dog. The malignant transformation of these neoplastic processes may occur which is correlated with advanced age and larger tumor size. (Moulton 1990)

References

1.  Peleteiro MC. 1994. Tumores mamários na cadela e na gata. Rev. Port. Ciência Vet. 89:10-34.

2.  Misdorp W, Else RW, Hellmén E, Lipscomb TP. 1999. Histological classification of mammary tumors of the dog and the cat. 2nd Series. v. VII. Washington DC, Arm. Forc. Inst. Pathol.

3.  American Registry of Pathology and the World Health Organization Collaborating Center for Worldwide Reference on Comparative Oncology, p.1-59.

4.  Sorenmno K. 2003. Canine mammary gland tumors. Vet. Clin. North Am. Small Anim. Pract. 33:573-596.

5.  Moulton JE. 1990. Tumors in Domestic Animals. 3rd edition. Berkley, University of California, p.518-552.