Canine Liposarcoma: What It Is and How It's Treated

Liposarcoma is a rare cancer of fat cells in dogs. It accounts for less than 0.5% of skin and subcutaneous tumors in dogs and cats (Forlani et al., 2015). It most often grows under the skin of the trunk and upper legs, but it can also arise in deeper tissues and in the spleen (Muscatello et al., 2024). Affected dogs are usually older, with a median age of 11 years in one study (Muscatello et al., 2024).

Liposarcomas are locally invasive but rarely spread to other organs (Baez et al., 2004). The most important factor in how long dogs live is how much tissue is removed with the tumor. In a study of 56 dogs, median survival was 1,188 days after wide excision, 649 days after marginal excision, and 183 days after biopsy alone (Baez et al., 2004).

A needle sample can't always tell fatty tumor types apart (Liptak, 2017), so a fatty lump that's changing or behaving unusually deserves a closer look before surgery.

Key points

• Liposarcoma is rare, making up less than 0.5% of skin and subcutaneous tumors in dogs and cats (Forlani et al., 2015).
• It usually grows under the skin of the trunk and upper limbs, and less often in deep tissue or the spleen (Muscatello et al., 2024).
• Wide excision gave the longest survival, and type of surgery was the only factor significantly linked to survival in a 56-dog study (Baez et al., 2004).
• The tumor came back locally in 12 of 43 dogs with follow-up (Baez et al., 2004).
• There are four subtypes, and the myxoid type may be a distinct disease with a preference for the spleen (Muscatello et al., 2024).
• A needle sample can confirm fat but can't tell a regular lipoma from an infiltrative one, and CT can help distinguish fatty tumor types (Liptak, 2017; Pendergrass, 2016).

Detailed explanation

Lipoma, infiltrative lipoma, or liposarcoma?

Fatty tumors in dogs fall into three main groups.

Lipomas are benign fatty lumps and are very common in dogs (Liptak, 2017). Our article on lumps that aren't cancer covers them.

Infiltrative lipomas are benign but locally aggressive, growing into normal muscle and fibrous tissue. They're common in the jaw and in the chest and belly walls, and the prognosis is guarded if they aren't treated aggressively (Liptak, 2017).

Liposarcomas are malignant tumors of fat cells. They're locally invasive but rarely spread (Baez et al., 2004).

These can be hard to tell apart. A fine-needle aspirate can diagnose a lipoma but can't distinguish the subtypes, so an incisional biopsy may be needed when a more aggressive tumor is suspected, and CT can also help (Liptak, 2017). In a CT study of 60 fatty tumors, liposarcomas were more likely than lipomas to look uneven on the scan, to contain nodules or mineral deposits, and to be linked with enlarged lymph nodes nearby (Pendergrass, 2016). Our articles on fine-needle aspirates and reading a pathology report explain these tests.

If your dog has a lump that feels firm and fixed rather than soft and movable, see our article on hard, immovable lumps on dogs.

Who gets liposarcoma

In a 2024 study of 51 dogs with liposarcoma, ages ranged from 6 to 16 years, with a median of 11. Male dogs outnumbered females 32 to 15. Most tumors (36) were under the skin, while a few were in muscle (3), inside a body cavity (2), or in the spleen (6) (Muscatello et al., 2024). In the 56-dog study, tumors were mainly on the limbs or along the body (Baez et al., 2004).

The four subtypes

Pathologists recognize four main subtypes of liposarcoma in dogs: well-differentiated, myxoid, pleomorphic, and dedifferentiated (Muscatello et al., 2024). In the 51-dog study, 26 were well-differentiated, 10 myxoid, 8 pleomorphic, and 7 dedifferentiated, and most were grade 1 or 2 (Muscatello et al., 2024).

Research suggests these subtypes may behave like different diseases. The myxoid subtype was linked to mutations in a gene called TP53 and to faster cell growth, and five of the six spleen tumors in the 2024 study were myxoid (Avallone et al., 2020; Muscatello et al., 2024). The authors concluded that canine myxoid liposarcoma may be a distinct disease with a preference for the spleen (Muscatello et al., 2024). In the 56-dog study, though, subtype didn't significantly affect survival (Baez et al., 2004), so this is an area where research is still developing.

Liposarcoma of the spleen

Liposarcoma of the spleen is uncommon. Among the non-blood-vessel, non-lymphoma sarcomas of the dog's spleen, liposarcomas make up 2% to 6% (Forlani et al., 2015). In a report of three dogs with myxoid liposarcoma of the spleen, all three later developed spread to the liver (Forlani et al., 2015). Our article on spleen tumors in dogs covers the more common causes of a splenic mass, and an abdominal ultrasound is often how these are found.

Treatment

Surgery is the main treatment, and how much tissue is removed matters most. The 56-dog study authors concluded that wide excision is preferred to marginal excision when feasible (Baez et al., 2004). In that study:

• 16 dogs had wide excision, with a median survival of 1,188 days
• 34 dogs had marginal excision, with a median survival of 649 days
• 6 dogs had only an incisional biopsy, with a median survival of 183 days
• Overall median survival was 694 days (Baez et al., 2004)

Interestingly, whether tumor cells were found at the surgical margins didn't significantly affect survival in that study, nor did tumor size, location, or subtype. Only the type of surgery did (Baez et al., 2004). That's a strong argument for planning the first surgery carefully, ideally with imaging beforehand, rather than removing the lump quickly as if it were a simple lipoma.

Liposarcoma is one of the soft tissue sarcomas, and our article on soft tissue sarcoma explains how these tumors are generally managed. Our guides to what clear margins mean and recovery after cancer surgery can help you prepare. If surgery is complex, asking about a referral to a veterinary oncologist or surgeon is reasonable.

Outlook

Survival was longest with wide excision (Baez et al., 2004). Local recurrence happened in 12 of 43 dogs with follow-up in the 56-dog study (Baez et al., 2004), so regular rechecks of the surgery site matter. Our article on whether cancer can return after treatment explains what to watch for. Liposarcomas in the spleen may behave more aggressively, based on a small case report (Forlani et al., 2015).

When to contact a veterinarian

Book an appointment soon if your dog has:

• A new lump of any kind, including one that feels fatty
• A fatty lump that's changing in size or feel
• A lump that has come back where one was removed before

Call the same day if your dog has a lump that's bleeding or ulcerated, or if your dog has a swollen belly, weakness, or pale gums.

Questions to ask your veterinarian

• Can we sample this lump before deciding on surgery?
• Could this be an infiltrative lipoma or a liposarcoma rather than a simple lipoma?
• Would CT or an incisional biopsy help plan surgery?
• Can we plan a wide excision the first time?
• What subtype and grade did the pathologist find?
• How often should we recheck the surgery site?

References

Avallone, G., Muscatello, L. V., Leoni, A., Roccabianca, P., Lepri, E., Crippa, L. [VERIFY: add remaining authors] (2020). p53 expression in canine liposarcoma correlates with myxoid variant and higher proliferative activity. Veterinary Pathology, 57(5), 620-622. 

Baez, J. L., Hendrick, M. J., Shofer, F. S., Goldkamp, C., & Sorenmo, K. U. (2004). Liposarcomas in dogs: 56 cases (1989-2000). Journal of the American Veterinary Medical Association, 224(6), 887-891. [VERIFY: confirm author list, volume, issue, pages, and add DOI]

Forlani, A., Roccabianca, P., Palmieri, C., Sarli, G., Stefanello, D., Santagostino, S., Randi, C., & Avallone, G. (2015). Pathological characterization of primary splenic myxoid liposarcomas in three dogs. Veterinary Quarterly, 35(3), 181-184. 

Liptak, J. M. (2017, March 6). Lipoma. Animal Cancer Surgeon. Retrieved November 10, 2026, from https://animalcancersurgeon.com/skin-tumors-lipoma

Muscatello, L. V., de Biase, D., Maloberti, T., di Oto, E., Tallini, G., Pellegrino, V., Bacci, B., Roccabianca, P., Lepri, E., Crippa, L., & Avallone, G. (2024). Analysis of MDM2 and TP53 genes in canine liposarcoma. Scientific Reports, 14, Article 14087. https://doi.org/10.1038/s41598-024-64963-z

Pendergrass, J. (2016, November 17). Computed tomography differentiates forms of adipose masses in dogs and cats. dvm360. https://www.dvm360.com/view/computed-tomography-differentiates-forms-of-adipose-masses-in-dogs-and-cats