Canis ISSN: 2398-2942


Contributor(s): Lori Ludwig, Kathryn Pratschke


  • Excision of mammary gland(s).


Surgical treatment of mammary neoplasia

  • Local excision/excisional biopsy/nodulectomy:
    • 'Lumpectomy', basically 'shelling out' tumor from gland with a narrow or non-existent margin of normal tissue.
    • Suitable for small, firm, moveable pea size nodules (less than 0.5 cm).
  • Local mastectomy:
    • En bloc removal of a single mammary gland.
  • Regional mastectomy:
    • Removal of two or more mammary glands with their associated lymph nodes. 
    • Originally based on a concept of vascular and lymphatic drainage that is potentially too simplistic given the known variation in lymphatic anatomy.
    • Glands 1, 2, 3 +/-4 drain to axillary and cranial sternal nodes.
    • Glands 3, 4, 5 +/-2 drain to the superficial inguinal nodes.
    • Unpredictable crossover of lymphatic branches between glands and also between right and left sides complicate this picture.
  • Unilateral radical mastectomy:
    • Unilateral  'mammary strip'.
    • Removal of all mammary glands on one side plus all associated lymph nodes.
  • Bilateral radical mastectomy:
    • Bilateral 'mammary strip'.
    • Removal of all mammary tissue plus associated lymph nodes.
    • May be performed as staged or simultaneous procedures.


  • Other than inflammatory carcinoma, surgical resection for mammary tumors Mammary gland: neoplasia. Inflammatory carcinoma is highly aggressive and rapidly metastatic, carrying an extremely poor prognosis. Surgery is unlikely to significantly influence outcome, but risks additional morbidity related to poor wound healing.
  • Although distant metastases are considered a contraindication to surgery, there may be cases where simple resection of a discrete ulcerated mass is warranted for palliation and quality of life reasons.
  • Local mastectomy is recommended for tumors that are centrally located within the gland and which are fixed to either underlying tissues or overlying skin. Approximately 2 cm lateral margins are recommended, with deep dissection to include abdominal muscle fascia and/or muscle if involved.
  • As mammary gland parenchyma tends to merge between glands 1, 2, and 3 and then again between glands 4 and 5, it will sometimes be easier to do regional mastectomy rather than try to divide parenchyma.
  • Regional mastectomy is recommended where tumors are eccentrically located, palpable in more than one gland or between glands. As with local mastectomy, 2 cm lateral margins are recommended.
  • Unilateral radical mastectomy is recommended if tumor is palpable in multiple glands along one chain; bilateral radical mastectomy can be performed where both sides are involved. Bilateral surgery can be done as a one-stage procedure, but many surgeons favor staging with a 4-6 week wait between procedures in order to reduce wound morbidity.
  • In dogs, there does not seem to be a clear survival advantage to radical mastectomy over regional mastectomy unless tumor growth involves the full length of the mammary chain.
  • For this reason, the approach favored by most surgeons is to use the simplest technique that allows removal of all neoplastic tissue, but not to routinely perform radical mastectomy for all mammary tumors.


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Negative prognostic markers

  • Increased age at time of diagnosis is associated with shorter overall survival in some studies but not in others.
  • Histopathological type: anaplastic carcinoma and sarcoma carry a poorer prognosis than simple carcinoma, which in turn has a worse prognosis than non-infiltrating carcinoma.
  • Histologic grading is significantly related to prognosis; this gives a measure of how biologically aggressive the disease is.
  • Low hormone receptor expression is associated with more aggressive tumors.
  • Tumor volume: tumors larger than 3 cm diameter have a decreased overall survival and tumors with lymph node metastases are often 5 cm diameter or larger.
  • Rapid growth rate.
  • Infiltration and invasive growth patterns (abdominal muscle, skin) and ulceration are all poor prognostic indicators.
  • Lymphatic or vascular invasion, distant metastasis: dogs with tumors at more advanced stage have a poorer outlook.
  • High Ki67, high Cox-2 expression and increased microvessel density have all been reported as negative factors but clinical validation is lacking currently.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Papazoglou L, Basdani E, Rabidi S et al (2014) Current Surgical Options for Mammary Tumor Removal in Dogs. J Vet Sci Med (2), 6 ResearchGate.
  • Sleeckx N, de Rooster H, Veldhuis Kroeze E J et al (2011) Canine Mammary Tumours, an Overview. Reprod Dom Anim 46 (6), 1112-1131 PubMed.
  • Sartin E A, Barnes S, Kwapien R P et al (1992) Estrogen and progesterone receptor status of mammary carcinomas and correlation with clinical outcome in dogs. Am J Vet Res 53 (11), 2196-200 PubMed.

Other sources of information

  • Lana S E, Rutteman G R & Withrow S (2007) Tumors of the Mammary Gland. In: Small Animal Clinical Oncology. Withrow S J & Vail D M. 4th edn. Elsevier, Chapter 26, pp 619-636.