Introduction

• Cause:
  • Correlated with uterine hyperplasia and adenocarcinoma Uterine adenocarcinoma, hypoestrogenism, prolactin-secreting pituitary adenomas.
  • Risk factors include aged (2 years +), multiparous, intact female rabbits.
• Signs:
  • Mammary gland enlargement, palpable masses in the mammary gland(s), often non-painful on palpation, may have discharge from the teat(s).
  • Rabbits are usually clinically active and alert, unless metastasis has occurred and they become cachexic, depressed and lethargic.
• Diagnosis: fine needle aspirate +/- biopsy.
• Treatment: mastectomy and ovariohysterectomy Ovariohysterectomy.
• Prognosis: dependent on +/- metastasis before diagnosis.

Print off the Owner Factsheets on Mammary gland adenocarcinoma, Common cancers, Caring for your rabbit before and after surgery, Neutering - why and when and Xray and Ultrasound to give to your clients.

Presenting signs

• Mammary gland(s) enlargement .
• Range from a small mass in a single gland to multiple coalescing firm masses in the mammary tissue.
• Usually not painful.
• +/- Brown-red sterile discharge from the teat(s).
• +/- Enlarged teat(s).
• +/- Hair loss around teat(s).
• No response to antibiotics.
• Localized mammary gland carcinoma:
  • Clinically bright, normal appetite and behavior.
  • Normal CBC Hematology & CHEM Blood biochemistry: overview.
• Metastasized mammary gland carcinoma (signs depend on how rapidly the carcinoma spreads):
  • Can be alert and active until shortly before death.
  • May be depressed, lethargic, inappetent, respiratory signs (if tumors have metastasized to the lungs) Respiratory: stertor / stridor, progressive weight loss Weight loss and cachexia (if undiagnosed for a long time).

Acute presentation

• Red-brown discharge from the teat(s).
• Palpable mammary enlargement +/- masses.
• Depressed and inappetent +/- cachexia (metastasis).

Age predisposition

• All ages of female rabbits are at risk; older, intact female rabbits are at higher risk.
• Risk increases with age.

Sex predisposition

• Primarily females - often multiparous but nulliparous are also at risk.
• Has not been reported in males, but theoretically can occur.

Breed predisposition

• Any breed is susceptible.
• Reports of familial mammary tumors in Belgian Belgian Hare and English English breeds.
• If the mammary carcinoma is linked to uterine adenocarcinoma, there is a breed predisposition for this Uterine adenocarcinoma.

Cost considerations

• If diagnosed early and without complications such as metastasis, surgery is curative.
• However, diagnostics often involve tests to rule out other underlying issues which may turn out to be costly.

Special risks, eg anesthetic

• High risk anesthesia Anesthesia: general if the carcinoma has already metastasized to the lungs.

Pathogenesis

Diagnosis

Treatment

Prevention

Sequelae

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Degner S, Schoon H A, Laik-Schandelmaier C et al (2018) Estrogen Receptor–α and Progesterone Receptor Expression in Mammary Proliferative Lesions of Female Pet Rabbits. Vet Pathol 55 (6), 838-848 PubMed.
• Baum B & Hewicker-Trautwein M (2015) Classification and epidemiology of mammary tumours in pet rabbits (Oryctolagus cuniculus). J Comp Pathol 152 (4), 291-298 PubMed.
• Walter B, Poth T, Böhmer E et al (2010) Uterine disorders in 59 rabbits. Vet Rec 166 (8), 230-233 PubMed.
• Blevins S, Gardner K, Wagner A et al (2009) Mammary gland enlargement and discharge in an adult New Zealand white rabbit. Lab Anim 38 (8), 258-261 PubMed.
• Sikoski P, Trybus J, Cline J M et al (2008) Cystic mammary adenocarcinoma associated with a prolactin-secreting pituitary adenoma in a New Zealand white rabbit (Oryctolagus cuniculus). Comp Med 58 (3), 297-300 PubMed.
• Saito K, Nakanishi M & Hasegawa A (2002) Uterine disorders diagnosed by ventrotomy in 47 rabbits. J Vet Med Sci 64 (6), 495-497 PubMed.
• Lipman N S, Zhao Z B, Andrutis K A et al (1994) Prolactin-secreting pituitary adenomas with mammary dysplasia in New Zealand white rabbits. Lab Anim Sci 44 (2), 114-120 PubMed.
• Greene H S (1939) Uterine adenomata in the rabbit; II. Homologous transplantation experiments. J Exp Med 69 (3), 447-466 PubMed.
• Greene H S (1939, 1940) Familial mammary tumors in the rabbit. I Clinical history. II. Gross and microscopic pathology. III. Factors concerned in their genesis and development. IV. The evolution of automony in the course of tumor development as indicated by transplantation experiments. J Exp Med 70 (2), 147-158; 159-166; 167-184; 71, 305-324 PubMed.
• Burrows H (1940) Spontaneous uterine and mammary tumours in rabbit. J Pathol Bacteriol 51, 385-390 VetMedResource.

Other sources of information

• Percy D H & Barthold S W (2007) Pathology of Laboratory Rabbits and Rodents. 3rd edn. Blackwell Publishing, USA. ISBN-13: 978-0-8138-2101-6/2007. pp 306-307.
• Paré J A & Paul-Murphy J (2004) Disorders of the Reproductive and Urinary Systems Disorders of the Mammary Gland; Cystic Mastitis, Mammary Dysplasia, and Mammary Tumours. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery (includes sugar gliders and hedgehogs). 2nd edn. Eds: Quesenberry K E & Carpenter J W. W B Saunders, USA. ISBN: 0-7216-9377-6. pp 187.
• Harcourt-Brown F (2002) Skin Diseases. In: Textbook of Rabbit Medicine. Butterworth-Heinemann, UK. ISBN: 0 7506-4002-2. pp 246.
• Weisbroth S H (1994) Neoplastic Diseases Tumors of the Mammary Gland. In: The Biology of the Laboratory Rabbit. 2nd edn. Eds: Manning P J, Ringler D H & Newcomer C E. Academic Press, USA. ISBN: 0-12-469235-4. pp 345-347.