Anal sac adenocarcinoma in Dogs (Canis) | Vetlexicon
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Anal sac adenocarcinoma

ISSN 2398-2942


Synonym(s): Tumor of the anal gland, anal sac carcinoma

Introduction

  • Anal sac disease is common in the dog (affecting ~12% of the population) but neoplasia is an uncommon clinical finding.
  • When neoplasia does occur, the majority of anal gland tumors are perianal adenomas Perianal neoplasia of intact male dogs.
  • The most common malignancy of the perineal region is adenocarcinoma of the apocrine glands (within the anal sac).
  • The tumor represents approximately 2% of canine skin neoplasms.
    Print off the owner factsheet Anal sac gland carcinoma to give to your client.

Presenting signs

  • Presenting signs of adenocarcinoma of the anal sac include those of local disturbance (perianal or anal distortion or swelling from the mass-effect within the gland), para-neoplastic (polyuria and polydipsia, or weakness, associated with hypercalcemia of malignancy) or metastatic effects (tenesmus, constipation and/stool shape change from metastasis to the sublumbar nodes).
  • May be detected unexpectedly during anal sac expression.
  • Rare: pelvic limb swelling, paraparesis, anorexia, foul odor from anal sacs.

Acute presentation

  • Perineal/anal area swelling (often ventrolateral to anus), intradermal or subcutaneous, often fixed by local invasion, hematochezia, abnormal self-grooming of the anal area/scooting.
  • Ulceration is rare.

Geographic incidence

  • None.

Age predisposition

  • In the canine, the adenocarcinoma of the anal sac is most common in pets between 7-12 years (median 10-11 years) with a range of 3-19 years.

Breed/Species predisposition

Cost considerations

  • Current treatment modalities for this condition include surgery with adjuvant modalities (chemotherapy and radiation) for metastatic disease. Treatments can be costly as can the morbidity from treatment.

Pathogenesis

Etiology

  • Malignant transformation of the apocrine components/glands located within the connective tissue stroma and near the fundic portion of the anal sac.

Predisposing factors

General

  • Breed, age (7-12 years) and possibly sex (female, neutered male).

Pathophysiology

  • Geotopical distribution of masses originate within the apocrine glands within the lining of the anal sac. There is a propensity of these tumors to metastasize to the regional (iliac/sub-lumbar) lymph nodes early. Later metastatic lesions appear within the liver, spleen, lungs and other sites.
  • In some animals, the space occupying effect of the mass is identified by the pet owner prompting consultation with a veterinarian. If a perianal swelling is not identified then a pet may simply present based on the effects of metastatic disease (stool shape change, paraparesis, tenesmus or constipation) or from paraneoplastic hypercalcemia (pseudo hyperparathyroidism-associated polyuria and polydipsia).
  • This is a highly invasive and metastatic tumor. In fact, the primary tumor burden in the pet may be incidental and barely palpable before metastatic disease is present. Because metastasis is generally, and initially, to the regional nodes, multimodality treatments (surgery with chemotherapy and/or radiation treatment) are generally favorable for median survivals beyond one year.
  • The neoplasm causes hypercalcemia by secretion of a parathyroid hormone-related protein (PTHrP PTHrP assay ) - humoral hypercalcemia of malignancy. This protein is seen in various normal tissues, presumably as a paracrine factor.
  • PTHrP stimulates osteoclastic bone resorption, increased renal tubular calcium reabsorption, and decreased renal tubular phosphate reabsorption.
  • Tumor removal typically allows calcium to return to normal (until metastatic disease recurs).

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.
  • Meier V, Polton G (2016) Outcome in dogs with advanced (stage 3b) anal sac carcinoma treated with surgery or hypofractionated radiation therapy. Vet Comp Oncol 15(3), 1073-1086 PubMed.
  • London C, Mathie T, Stingle N et al (2012) Preliminary evidence for biologic activity of toceranib phosphate (Palladia®) in solid tumors. Vet Comp Oncol 10, 194-205 PubMed.
  • Polton G A & Brearley M J (2007) Clinical stage, therapy, and prognosis in canine anal sac gland carcinoma. J Vet Int Med 21, 274-280 PubMed.
  • Hobson H P, Brown M R & Rogers K S (2006) Surgery of metastatic anal sac adenocarcinoma in five dogs. Vet Surg 35, 267-270 PubMed.
  • Emms S G (2005) Anal sac tumours of the dog and their response to cytoreductive surgery and chemotherapy. Aust Vet J 83, 340-343 PubMed.
  • Llabres-Diaz F J (2004) Ultrasonography of the medial iliac lymph nodes in the dog. Vet Radiol Ultrasound 45, 156-165 PubMed.
  • Williams L E, Gliatto J M, Dodge R K, Johnson J L, Gamblin R M, Thamm D H, Lana S E, Szymkowski M & Moore A S (2003) Carcinoma of the Apocrine Glands of the Anal Sac in Dogs: 113 cases (1985-1995). JAVMA 223, 825-831 PubMed.
  • Bennett P F, DeNicola D B, Bonney P, Glickman N W & Knapp D W (2002) Canine Anal Sac Adenocarcinoma: Clinical Presentation and Response to Therapy. J Vet Intern Med 16, 100-104 PubMed.
  • Ross J T, Scavelli T D, Matthiesen D T & Patnaik A K (1991) Adenocarcinoma of the Apocrine Glands of the Anal Sac in Dogs: A Review of 32 cases. J Am Anim Hosp Assoc 27 (3), 349-355 VetMedResource.
  • Meuten D J, Cooper B J, Capen C C, Chew D J & Kociba G J (1981) Hypercalcemia Associated with an Adenocarcinoma Derived from the Apocrine Glands of the Anal SacVet Pathol 18 (4), 454-471 PubMed.

Other sources of information

  • Goldschmidt M H & Hendrick M J (2002) Ch. 2 Tumors of the Skin and Soft Tissues. In: Meuten D J (ed.) Tumors in Domestic Animals.4th Edn. Iowa State Press, Iowa ISBN 0-8138-2652-7, pp 74-76 and pp 672-679.
  • Goldschmidt M H & Shofer F S (1992) Skin Tumors of the Dog and Cat. 1st edn. Pergamon Press Oxford UK, pp 103-108.