Unexpected finding in dog with new asymptomatic III/VI murmur

PATIENT INFORMATION:

Age: 11year

Gender: Female Spayed

Species: Canine

Breed: Border Collie Mix

Weight: 40.6lbs

HISTORY:

New III/VI murmur noted at annual exam. No exercise intolerance, cough, or other signs of cardiac disease.

INITIAL ECHOCARDIOGRAM ANALYSIS:

A moderate sized, pedunculated mass was identified within the right ventricular outflow(RVOT) just below the pulmonic valve. Additionally, mild chronic degenerative valve disease (stage B1) resulting in mild mitral regurgitation and tricuspid regurgitation.

RECHECK ECHOCARDIOGRAM ANALYSIS(11 months post initial diagnosis):

Minimal change in the RVOT mass(suspected ectopic thyroid tumor). (25 x 19mm; previously 25 x 18mm) Increasing RVOT velocities (increased to 2.4 m/s from 1.8m/)) suggesting the development of mild obstruction.

ADDITIONAL DIAGNOSTICS:

Abdominal ultrasound was performed a month after the initial echocardiogram. Single ill-defined nodule(likely benign change) noted in the spleen and unilateral adrenomegaly identified.

DIAGNOSIS:

RVOT neoplasia.

Though uncommon in general, cardiac masses are typically found to be hemangiosarcoma, aortic body tumours ( most commonly chemodectoma), lymphoma and ectopic thyroid carcinomas. Numerous other cardiac tumors(including myxoma, sarcomas and metastatic lesions) have been described in case reports but are rare.

Ectopic thyroid tumors are often identified within the RVOT and are associated with the embryologic development of thyroid and right ventricular outflow tract.

CASE OUTCOME:

The patient continues to do well clinically with no clinical signs beyond a cardiac murmur. A monitoring echocardiogram is upcoming. No therapies have been initiated and the owner has elected monitoring at this time.

PROGNOSIS/DISCUSSION:

Given the location, ectopic thyroid carcinoma was initially suspected but minimal progression has opened the possibility of other tumor types. A biopsy of the mass is needed for a definitive diagnosis.

The expected prognosis as the mass grows is poor as RVOT obstruction will eventually develop which will lead to right sided congestive heart failure. Minimal change over 11 months hopefully means this is a slow growing tumor type and the time to onset of right heart failure will be long.

Additional therapeutic options could include radiation therapy to slow tumor growth or reduce tumor size of the mass and stenting the RV outflow tract when needed.