ISSN 2398-2969      

Mammary gland: neoplasia

icanis

Introduction

  • 25% of all canine tumors (50-70% of tumors in all sites in bitches).
  • Second most common tumor in bitches after skin tumors. Most common tumor in sexually intact bitches.
  • 40% malignant.
  • Benign, carcinomas, sarcomas: of interstitial connective tissue, myoepithelial cells peripheral to ducts or alveoli, ductar epithelium.
  • Cause: progestagen administration increases incidence of benign tumors and mammary hyperplasia, progestagen and estrogen increase the risk of malignant tumors; some show marked estrus-related growth.
  • Signs: various. Most dogs develop tumors in multiple glands.
  • Diagnosis: signs, histopathology.
  • Treatment: surgery if no evidence of pulmonary metastasis and/or chemotherapy if high grade of malignancy and/or metastatic disease.
  • Prognosis: favorable if complete excision, low grade, and no evidence of metastasis.
  • Prevention: ovariohysterectomy before puberty.
    Print off the owner factsheet on Breast cancer in dogs to give to your client.

Pathogenesis

Etiology

  • Mammary tumors develop from benign to malignant tumors as part of a continuum influenced by hormones.
  • Mixed mammary tumor (fibroadenoma) - benign.
  • Mammary adenocarcinoma (tubular and papillary) - malignant but less so than anaplastic carcinomas.
  • Mammary sarcoma - rare.

Predisposing factors

General
  • Elderly dogs.
  • Hormonal - estrus cycle.
    Ovariohysterectomy prior to first estrus reduces risk of developing mammary tumor to 0.5%.
    Ovariohysterectomy prior to the second estrus reduces risk of developing mammary tumor to 8%.
    Ovariohysterectomy prior to the third estrus reduces risk of developing mammary tumor to 26%.
  • No benefit after 4 years of age.
  • Body weight: being underweight at puberty provides protection against later tumor development; obesity at young age and a diet high in red meat increases the risk of developing a mammary tumor.

Specific

  • Progestagen and estrogen administration: increases incidence of mammary tumors. Low-dose progestagen alone increases the risk for hyperplasia and benign tumors, a combination of estrogen and progestogen increases the risk of malignant tumors.
  • Possible role of BRCA gene and of HER2/erb-2 (epidermal growth factor receptor).

Pathophysiology

  • During first few estrus cycles -> small clones of preneoplastic epithelial cells established -> true neoplasms after many years.
  • Approximately 50% of malignant mammary tumors are thought to have estrogen and/or progesterone (ER + PR) receptors and some exhibit marked estrus-related growth.
  • Higher incidence (70%) of ER + PR in benign tumors and normal glands.
  • Dogs that are younger, in estrus, and intact are more likely to have receptor-positive tumors than dogs that are older, spayed, and/or in anestrus.
  • Hormone receptor expression is inversely correlated to size (large tumors), histopathology (high grade tumors), and presence of metastatic disease.

Timecourse

  • Usually chronic course, months-years.
  • Very malignant tumors may be more rapidly growing.

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • de Araújo M R, Campos L C, Ferreira E, Cassali G D (2015) Quantitation of the regional lymph node metastatic burden and prognosis in malignant mammary tumors of dogs. JVIM 29 (5), 1360-1367 PubMed.
  • Lim H Y et al (2015) Effects of obesity and obesity-related molecules on canine mammary gland tumors. Vet Pathol 52 (6), 1045-1051 PubMed.
  • Tran C M, Moore A S, Frimberger A E (2014) Surgical treatment of mammary carcinomas in dogs with or without postoperative chemotherapy. Vet Comp Onc 14 (3), 252-262 PubMed.
  • Kristiansen V M et al (2013) Effect of ovariohysterectomy at the time of tumor removal in dogs with benign mammary tumors and hyperplastic lesions: a randomized controlled clinical trial. J VIM 27 (4), 935-942 PubMed.
  • Sorenmo K U et al (2009) Canine mammary gland tumours: a histological continuum from benign to malignant; clinical and histopathological evidence. Vet Comp Oncol (3), 162-172 PubMed.
  • Chang S C et al (2005) Prognostic factors associated with survival two years after surgery in dogs with malignant mammary tumors: 79 cases (1998-2002). JAVMA 227 (10), 1625-1629 PubMed.
  • Karayannopouloua M et al (2005) Histological grading and prognosis in dogs with mammary carcinomas: application of a human grading method. J Comp Pathol 133 (4), 246-252 PubMed.
  • Pérez Alenza D, Tabanera E, Peña L (2001) Inflammatory mammary carcinoma in dogs: 33 cases (1995-1999). JAVMA 219 (8), 1110-1114 PubMed.
  • Stockhaus C, Kohn B, Rudolph R, Brunnberg L & Giger U (1999) Correlation of hemostatic abnormalities with tumor stage and characteristics in dogs with mammary carcinoma. JSAP 40 (7), 326-331 PubMed.

Other sources of information

  • Sorenmo K U, Worley D R, Goldschmidt M H (2013) Tumors of the mammary gland. In:Small Animal Clinical OncologyEds. S J Withrow, D M Vail, R L Page. 5th ed. Philadelphia: W B Saunders. Chapter 27 pp 538-547.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!