A dog presenting for acute illness associated with a splenic mass is commonplace in small animal practice. The typical scenario is that of an older, large breed dog that has become acutely weak or may have had chronic, non-specific signs of illness culminating in an emergent situation. These dogs often have bleeding into the abdomen associated with the rupture of the mass.
In addition to the various interventions needed to stabilize and support these patients, surgery is often indicated to remove the diseased spleen (splenectomy), and often this decision to proceed to surgery needs to be made quickly. The challenge for veterinarians and for pet owners in this situation is trying to determine whether the dog may have a malignant splenic tumor or a benign mass.
The most common malignancy of the spleen is hemangiosarcoma. This tumor type is highly metastatic and has a poor long-term prognosis. Dogs that have a splenic hemangiosarcoma and that undergo surgery typically only live an additional two to three months postoperatively. Conversely, the most common benign mass of the spleen in dogs (a hematoma) is typically curative with a splenectomy.
Chest radiographs and other imaging can be helpful for assessing a dog for metastases. If metastases are not evident, however, we are left with an inability to reliably distinguish whether a given dog has a benign versus malignant mass of the spleen.
We tend to generalize about the probabilities of splenic mass malignancy based on retrospective analyses of large populations of dogs. The "law of two-thirds" implies a ~60 percent probability that a splenic tumor is malignant versus benign. Additionally, approximately two-thirds of those malignancies are determined to be hemangiosarcoma. Not every dog with a splenic mass, however, has a ~60 percent probability of malignancy (hemangiosarcoma). As such, it's really difficult for veterinarians to guide an owner about the best course of action (surgery or no surgery).
Anyone in this situation would most want to avoid making a decision to euthanize a dog that has a benign splenic mass and a reasonable likelihood of recovery. On the other hand, if an owner was given a reliable indication that their dog might have a hemangiosarcoma (or other malignancy), they might elect humane euthanasia rather than subjecting their animal to surgery in light of a poor long-term prognosis.
An online decision-support calculator (T-STAT) has been developed to assist veterinarians and pet owners in determining the probability of splenic mass malignancy for an individual dog. This tool, which was recently made available, uses information commonly collected soon after admission including bloodwork and abdominal ultrasound findings. It may facilitate owner decisions to proceed with surgery (or not) and has the potential to reduce the risk of an erroneous decision to euthanize a dog that could otherwise be cured by the surgical removal of a benign mass.
Dr. John Berg, DVM, MS, DACVS - a board certifed veterinary surgeon at Tufts University - recently spoke to us about splenic masses and the applications of this online calculator. View this video now compliments of VetVine (running time: 16 mins; veterinarians and veterinary technicians are eligible to earn CE credit on a pay-per-view basis or inclusive of a VetVine Premium Membership).
