Fatty tumors, called lipomas, are firm, movable growths that develop under a dog’s skin. At times, these tumors become invasive, developing into infiltrative lipomas. Both types of lipomas are benign, differing from the malignant liposarcoma. A needle biopsy is required to tell the difference between benign and malignant tumors. While a benign tumor will not typically become malignant, benign and malignant tumors can exist on the same dog at the same time.
The majority of soft, fatty tumors are benign, painless masses that form in the tissue under the skin. These tumors are called lipomas. They will never become malignant and typically do not have to be removed. On occasion, lipomas become invasive and burrow their way into other tissues. Although these masses are not malignant, they can cause your dog distress or discomfort when moving. These infiltrative lipomas require surgery to remove them and sometimes radiation therapy to treat them. Liposarcomas are malignant fatty tumors. They are fast-growing and aggressive masses that spread to other tissues in the dog’s body. Liposarcomas begin as cancerous masses. They are not lipomas that have become cancerous. They can kill your dog if they are not removed and treated. These tumors can become extremely large and frequently grow back even if removed.
Mast cell tumors and hemangiopericytomas are not fatty tumors, although they feel superficially similar to the touch. Both of these tumors are malignant and are life-threatening to your dog. It is necessary to perform a needle biopsy on the tumor to determine the nature of any soft tumor to determine if it is cancerous or not.
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