From Dog
Synovial myxoma in the stifle of a dog, showing multiple myxomatous islands of variable sizes separated by collagenous septa[1]

Myxomas are a benign neoplasia of connective tissue.

These tumors are slow growing and locally destructive tumors and can affect various organs such as blood vessels (angiomyxoma), joint tissue (synovial myxoma), kidneys, heart, teeth (odontogenic) or bone.

Angiomyxomas are relatively rare and locally invasive and have been reported in the canine kidney, causing chronic renal disease[2].

Synovial myxomas are common in large-breed dogs and affect the synovial cartilage of the stifle and digits[1][3].

Odontogenic myxomas have a similarly good prognosis although surgical debridement or manbidulectomy may be required in advanced cases[4].

Cardiac myxomas often arise on the tricuspid heart valves and slowly lead to congestive heart failure[5][6].

A tentative diagnosis can be made on ultrasonographic or radiographic appearance of these growths which may have mineralization as part of their neoplastic changes.

Diagnosis is based on histological examination of tissue samples. These tumors have a characteristic appearance with spindle cells in loosely packed and interlacing streams within a myxomatous stroma. The myxomatous nature of the tumors is usually confirmed by positive staining with Alcian blue and vimentin.

A differential diagnosis would include hemangiosarcoma, lymphoma and histiocytoma.

Immunohistochemical staining is usually positive for vimentin, von Willebrand Factor, and alpha-smooth muscle actin.

With odontogenic myxomas, surgical extirpation is usually curative, but angiomyxomas and synovial myxomas tend to progressively worsen, with survival rates of 1 - 2 years depending on location. Cardiac myxomas are usually untreatable in the veterinary setting without bypass machines allowing surgical replacement of the defective valve.


  1. 1.0 1.1 Craig LE et al (2010) Canine synovial myxoma: 39 cases. Vet Pathol 47(5):931-936
  2. Gajanayake I et al (2010) Paraneoplastic hypercalcemia in a dog with benign renal angiomyxoma. J Vet Diagn Invest 22(5):775-780
  3. Berrocal A et al (2001) A joint myxoma in a dog. J Comp Pathol 124(2-3):223-226
  4. Meyers B et al (2007) Diagnosis and management of odontogenic myxoma in a dog. J Vet Dent 24(3):166-171
  5. Akkoc A et al (2007) Valvular cardiac myxoma in a dog. J Vet Med A Physiol Pathol Clin Med 54(7):356-358
  6. Machida N et al (2003) Cardiac myxoma of the tricuspid valve in a dog. J Comp Pathol 129(4):320-324