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Mammary gland: neoplasia
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.
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Presenting signs
- Palpable mass(es) in mammary gland.
- Abnormal mammary secretion.
- Weight loss.
- Ulceration of overlying skin
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Acute presentation
- Rapidly spreading, ulcerating mass(es) invading the surrounding skin would be typical of malignant masses.
- 'Blue dome' appearance - blue raised area in mass.
Age predisposition
- Middle to old aged.
- 10-12 years mean age occurrence. May occur at younger age in Siamese Siamese.
- Risk increases with age but becomes significant after 7-9 years.
Breed/Species predisposition
- ?Siamese Siamese at increased risk - although no proven breed predilection. May occur at younger age in Siamese.
Pathogenesis
Predisposing factors
General
- Hormonal - estrous cycle.
- Cats spayed prior to 6 months of age have 91% less 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 mammary 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.