ISSN 2398-2950      

Mammary gland: neoplasia

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Introduction

  • Third most common tumor in cats after hematopoietic and skin tumors; incidence of 25 per 100,000 females and 12% of feline tumors regardless of sex. 85-95% are malignant.
  • Benign tumors, carcinomas, sarcomas of interstitial connective tissue, myoepithelial cells peripheral to ducts or alveoli, and ductar epithelium. >80% are adenocarcinomas.
  • Signs: mammary mass(es), sometimes with associated discharge. Weight loss.
  • Incidence highest in middle aged or older cats. Occasionally seen in males.
  • Treatment: surgery if no evidence of pulmonary metastasis. +/- Chemotherapy depending on histopathology results.
  • Prognosis: good with benign tumors; guarded to poor with malignancies.
  • Prevention: ovariohysterectomy Ovariohysterectomy before puberty.
    Print off the owner factsheet Breast cancer in cats Breast cancer in cats to give to your client.

Pathogenesis

Predisposing factors

General

  • Hormonal - estrous cycle.
  • Cats spayed prior to 6 months of age have 91% risk of developing a mammary tumor.
  • Cats spayed between 7 and 12 months of age have 86% less risk of developing a mammary tumor.
  • Cats spayed between 13 and 24 months of age have 11% less risk of developing a mammary tumor. No benefit is seen after 24 months.

Specific

  • Progestins increase the incidence of mammary hypertrophy, which may result in the development of benign tumors or carcinomas.
  • A-type and C-type retrovirus have been isolated from feline mammary tumors. Significance unknown.

Pathophysiology

  • Small clones of preneoplastic epithelial cells established during first few estrous cycles   →   true neoplasms after many years.
  • Approximately 20-40% of mammary tumors are thought to have estrogen receptors and some exhibit marked estrus-related growth. 40% of feline malignant tumors express progesterone receptors.
  • HER-2/neu (epidermal growth factor receptor) expression is reported in 5.5-90% feline mammary tumors.
  • Benign tumors include adenomas, fibroadenomas, lipomas and duct papillomas. 
  • Malignant tumors are mostly epithelial in origin, mainly adenocarcinomas (divided between tubular and papillary). Sarcomas are rare.

Timecourse

  • Weeks to months.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mills S W, Musil K M, Davies J L et al (2015) Prognostic value of histologic grading for feline mammary carcinoma: a retrospective survival analysis. Vet Pathol 52 (2), 238-249 PubMed.
  • Zappulli V, Rasotto R, Caliari D et al (2015) Prognostic evaluation of feline mammry carcinomas: a review of the literature. Vet Pathol 52 (1), 46-60 PubMed.
  • Matos A  J, Baptisa C S, Gärtner M F et al (2012) Prognostic studies of canine and feline mammary tumours: The need for standardized procedures. Vet J 193 (1), 24-31 PubMed.
  • Seixas F, Palmeira C, Pires M A et al (2011) Grade is an independent prognostic factor for feline mammary carcinomas: A clinicopathological and survival analysis. Vet J 187 (1), 65-71 PubMed.
  • Dias Pereira P & Gärtner F (2003) Expression of E-cadherin in normal, hyperplastic and neoplastic feline mammary tissue. Vet Rec 153 (10), 297-302 PubMed.
  • Hahn, K A & Adams W H (1997) Feline mammary neoplasia: biological behaviour, diagnosis and treatment alternatives. Feline Pract 25 (2), 5-11 VetMedResource.

Other sources of information

  • Sorenmo K U, Worley D R, Goldschmidt M H (2013) Tumors of the mammary gland. In: Small Animal Clinical Oncology. Eds S J Withrow, D M Vail, R L Page. 5th edn. Chapter 27, pp 547-552. Philadelphia: W B Saunders.
  • Oglivie, K & Moore, A S (1995) Managing the Cancer Patient. Veterinary Learning Systems pp 434-440.

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