Myomas (Rhabdomyomas and Leiomyomas) in Dogs and Cats
📝 Summary
Myomas are muscle tumors including rhabdomyomas and leiomyomas that may be benign or malignant; dogs most often show malignant rhabdomyosarcoma with a possibly hereditary cause. They can occur in any muscle organ and are hard to remove once invasive, so anti-cancer medication is used.
1 Symptoms
Rhabdomyomas may be single or multiple, small or huge, flat or round, with a tendency to spread diffusely and infiltrate, showing no clear border with surrounding tissue. They form slowly but can grow quite large.
Whether benign or malignant, rhabdomyomas can arise in nearly any organ that contains muscle tissue, so signs depend on the location involved.
2 Causes and Transmission
Myomas are not contagious. In dogs the malignant rhabdomyosarcoma is the form usually seen; the cause is unclear but may relate to heredity, and either sex of any breed can be affected.
Leiomyomas, the benign smooth-muscle form, are addressed separately. No infectious agent is involved.
3 Diagnosis
A veterinarian evaluates the affected organ with imaging and takes a tissue or cell sample to identify the tumor type and whether it is benign or malignant.
Because myomas in different tissues mimic other diseases, recurring or hard-to-treat signs should prompt thorough testing to rule out a tumor.
4 Treatment
Once a myoma invades surrounding tissue, surgery is difficult. If it has spread, the outlook is poor. Malignant forms are managed with anti-cancer medication to slow progression.
Even benign myomas need monitoring to prevent continued growth or spread.
5 Prevention
There is no specific prevention. Because some forms may be hereditary, affected animals should not be bred.
Prompt investigation of persistent or recurring symptoms in any organ helps detect muscle tumors before they become inoperable.
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