An 81-year-old man referred for pneumonia ended up with an unexpected heart problem. A CT scan picked up a mass about 7.6 centimeters long bulging from his right ventricle, the chamber that pumps blood to the lungs. It was filled with blood, connected to the heart through several narrow slits, and looked like an aneurysm, a dangerous outpouching of the heart wall.
It was actually a lipoma, a benign fatty tumor, and one that had taken on a strikingly deceptive shape. Surgeons at Gifu University Hospital in Japan removed it and described the case on Aug. 30 in Case Reports in Surgery.
The man had no symptoms before the operation. But pressure measurements inside his heart suggested the mass was already straining it, and at its thinnest point, its wall was only 3 millimeters thick.
A Mass That Swelled and Shrank with Every Heartbeat
The man was being treated for high blood pressure and diabetes when his primary care doctor referred him for pneumonia. The CT scan that followed found an abnormal mass in his mediastinum, the space between the lungs, measuring 47 by 76 millimeters.
Contrast imaging showed the mass protruding from the right ventricle with a blood-filled cavity and multiple slit-like channels linking it to the chamber. Density readings on the scan indicated that much of the mass was fat, which led the team to suspect a lipoma early on.
An echocardiogram added a strange detail. Blood flowed back and forth between the ventricle and the mass, which expanded as the ventricle squeezed and contracted as it relaxed. The mass was also compressing and deforming the right atrium, the chamber above.
Catheter measurements showed pressures of 12 mmHg in the right atrium and 25 mmHg in the right ventricle at the end of filling, readings the authors described as elevated. His coronary arteries were normal, and he had no history of trauma or heart attack, the usual causes of a false aneurysm, or pseudoaneurysm, in this chamber.
Surgeons Prepared for the Worst Before Opening the Chest
Although he had no symptoms, the team decided to operate. The thin wall raised concern about rupture, the elevated pressures suggested early strain, and imaging alone could not rule out other diagnoses.
Because the mass sat directly behind the breastbone, surgeons worried it could be stuck to the bone and that cutting through the sternum might trigger fatal bleeding. So before opening the chest, they connected him to a heart-lung machine through an artery near his right armpit and a vein in his groin.
The precaution turned out to be unnecessary, since there were no adhesions. Surgeons found a soft, yellowish, fat-covered mass bulging from the front wall of the right ventricle, with blood flowing through it. They removed all of the fatty tissue until healthy heart muscle was exposed, leaving a hole about 3 centimeters wide that they repaired with fabric patches.
The removed mass measured 85 by 60 by 50 millimeters. Under the microscope, its wall was made of fat cells with no heart muscle cells at all, and its inner cavity was lined with endothelial cells, the type that normally lines blood vessels.
He recovered without complications and went home 14 days after surgery. Follow-up catheterization showed the pressure in his right ventricle had dropped from 25 to 4 mmHg.
A Rare Tumor in an Even Rarer Spot
Cardiac lipomas account for about 8.4% of benign tumors that start in the heart, according to the case report. The right ventricle is an unusual home for them. The authors cite a review of 208 cardiac lipoma cases in which only 10 were found in that chamber.
Most cardiac lipomas cause no symptoms and are found by accident. Those that grow into a heart chamber can obstruct blood flow, contribute to heart failure or disrupt the heart's electrical system.
A handful of lipomas that mimic aneurysms have been reported. They include a right ventricular lipoma described in 2000in The Annals of Thoracic Surgery that communicated with the ventricle, and a large cardiac lipoma with a pseudoaneurysm-like appearance reported in the Journal of the American College of Cardiology in 2012. A 2010 case of an extensive lipoma was associated with an aneurysmal right ventricle.
Doctors Still Can't Say How It Took This Shape
The authors do not know how a fatty tumor came to look and behave like an aneurysm. They offer two hypotheses. A lipoma growing from part of the ventricle wall may have gradually expanded until pressure from inside the chamber pushed blood into it. Alternatively, new blood vessels may have formed within the tumor and eventually connected to the ventricle.
Both ideas remain speculative. The man had no earlier CT scans or echocardiograms, so there was no way to track how the mass developed.
There are also no standardized guidelines for treating cardiac lipomas. Small, symptom-free lipomas that do not affect blood flow are often monitored rather than removed, while large ones causing symptoms or strain on the heart are generally considered for surgery. The Gifu team argues that surgery can be reasonable even without symptoms when a lipoma has an unusual shape, raises pressure inside the heart, or leaves the diagnosis uncertain. As a single case, the report cannot establish how often that approach is needed or how patients fare over the long term.
People who learn of an incidental heart mass on a scan should discuss follow-up imaging and treatment options with a cardiologist.
Key Questions Answered
What did doctors find in the man's heart?
A benign fatty tumor, or lipoma, bulging from the right ventricle. It contained a blood-filled cavity connected to the chamber, which made it look like an aneurysm on scans.
How was it discovered?
Incidentally, on a CT scan performed after he was referred for pneumonia.
Why did surgeons operate if he had no symptoms?
The tumor's wall was as thin as 3 millimeters, raising concern about rupture. Pressures in his right heart were elevated, and imaging could not fully confirm the diagnosis.
How did he do after surgery?
He recovered without complications, went home 14 days later, and his right ventricular pressure fell from 25 to 4 mmHg.
How rare is a lipoma in the right ventricle?
Very rare. One review cited by the authors found only 10 right ventricular cases among 208 cardiac lipomas.
