Large study links canine splenic myelolipomas to rupture risk
Bottom line
Myelolipomas, long considered mostly incidental benign lesions in dogs and cats, may carry more clinical weight in canine spleens than the literature has suggested. In a newly published retrospective study in Veterinary Pathology, investigators reviewed 2,697 myelolipoma cases and found that 96.3% were in dogs and 3.7% in cats. In dogs, nearly all lesions were splenic, and splenic hematoma arising from myelolipoma was reported in 39.8% of cases, with significantly higher odds of both hemoabdomen and splenic rupture compared with cases without hematoma. Cats looked different: splenic hematoma, hemoabdomen, and rupture were uncommon, and about half of feline hepatic myelolipomas arose within peritoneopericardial diaphragmatic hernias. (lifescience.net)
Why it matters: For veterinary professionals, the study challenges the assumption that splenic myelolipoma is always an incidental, low-concern diagnosis in dogs. The findings suggest that when myelolipoma is linked with splenic hematoma, clinicians may need to think more carefully about rupture risk, hemoabdomen, case triage, and client communication. That’s especially relevant in emergency settings, where ruptured splenic masses are often presumed malignant, even though prior canine splenic mass studies have shown a meaningful benign subset after splenectomy. (lifescience.net)
What to watch: Watch for follow-up discussion on whether these data change how pathologists report splenic myelolipomas and how clinicians counsel pet parents about monitoring versus surgery in dogs. (lifescience.net)
Key facts
- Study type
- Retrospective study
- Journal
- Veterinary Pathology
- Cases reviewed
- 2,697 myelolipoma cases
- Species split
- 96.3% dogs, 3.7% cats
- Dogs, main site
- 98.2% of lesions were splenic
- Dogs, hematoma rate
- Splenic hematoma arose in 39.8% of canine cases
- Dogs, complication risk
- Higher odds of hemoabdomen and splenic rupture with hematoma
- Cats, hepatic association
- About half of feline hepatic myelolipomas arose within peritoneopericardial diaphragmatic hernias
A large new retrospective study is putting canine and feline myelolipomas back on the clinical radar. Writing in Veterinary Pathology, researchers analyzed 2,697 cases and found that, in dogs, splenic myelolipomas were commonly associated with hematoma formation and carried significantly increased odds of hemoabdomen and splenic rupture. That stands out because myelolipomas are generally described as benign proliferations of adipose and hematopoietic tissue, and are often treated as incidental findings. (lifescience.net)
That benign framing has shaped the literature for years, in part because published veterinary reports have been sparse and often limited to case reports or small series. The new paper addresses that gap with a much larger dataset, allowing the authors to look at signalment, anatomic distribution, and clinical associations in a way earlier reports could not. Prior feline literature, for example, has described splenic and hepatic myelolipomas as rare, with management questions still unresolved and evidence for surgery versus conservative monitoring remaining thin. (lifescience.net)
The study’s core findings were species-specific. Of the 2,697 total cases, 2,596 were dogs and 101 were cats. In dogs, Labrador retrievers were the most affected breed, mean age at diagnosis was 11.4 years, mean mass diameter was 7.4 cm, and the spleen accounted for 98.2% of lesions, with the adrenal gland a distant second at 1.3%. In cats, domestic shorthairs made up 53.5% of cases, mean age was 11.1 years, mean mass size was 2.4 cm, and the spleen and liver were the main sites. In feline cases, half of hepatic myelolipomas occurred within peritoneopericardial diaphragmatic hernias. (lifescience.net)
The most practice-relevant signal was in dogs with splenic hematoma arising from myelolipoma. Those cases made up 39.8% of canine cases and were associated with markedly higher rates of hemoabdomen, 11.8% versus 2.0%, and splenic rupture, 13.9% versus 3.5%. The reported odds ratios were 6.138 for hemoabdomen and 3.898 for splenic rupture, both with P values below 0.001. By contrast, the same complications were infrequent in cats. (lifescience.net)
Outside this study, the broader splenic mass literature helps frame why that matters clinically. Prospective work in dogs with ruptured splenic tumors has shown that benign lesions are not rare in spontaneous hemoperitoneum cases, and a more recent JAVMA cohort also identified myelolipoma among secondary benign diagnoses in dogs undergoing splenectomy for splenic rupture. Meanwhile, a 2024 feline review concluded that splenectomy may be reasonable in symptomatic cats with splenic myelolipoma, but emphasized that optimal management is still unknown. (doi.org)
Why it matters: For veterinarians, the paper sharpens a diagnostic nuance. “Benign” does not necessarily mean clinically irrelevant, particularly in older dogs with splenic lesions, anemia, abdominal bleeding, or imaging findings that could fit hematoma or rupture. The study may influence how clinicians interpret splenic differentials, how pathologists contextualize myelolipoma in reports, and how emergency and surgery teams discuss prognosis with pet parents when a ruptured splenic mass has not yet been fully characterized. It also reinforces a species divide: canine splenic myelolipomas may deserve closer attention, while feline lesions still appear less likely to present with rupture or hemoabdomen, though hepatic lesions in cats should raise awareness of possible PPDH associations. (lifescience.net)
There doesn’t appear to be a press release or formal society statement attached to the paper yet, and expert commentary was limited at the time of writing. Still, the size of the dataset alone is likely to make this study a reference point in future discussions of splenic pathology and hemoperitoneum risk in small animal practice. (lifescience.net)
What to watch: The next question is whether these retrospective findings translate into changes in case management, especially around surgical decision-making, pathology reporting language, and risk counseling for dogs with splenic myelolipomas and concurrent hematoma. Prospective outcome data would be the logical next step. (lifescience.net)