Cardiac undifferentiated pleomorphic sarcomas are highly malignant mesenchymal tumors of the heart.
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Terminology
Terms that are no longer recommended for use include ‘intimal sarcoma’, ‘undifferentiated sarcoma’ and ‘undifferentiated spindle cell sarcoma’ 1.
Epidemiology
Cardiac undifferentiated pleomorphic sarcomas are rare primary malignant tumors of the heart that account for a substantial number of cardiac sarcomas 1-3. There is no gender predominance and the mean age of presentation is in the sixth decade 1.
Diagnosis
The diagnosis is based on the histological features 1. However, a malignant appearing infiltrative polypoid tumor located in the left atrium might pose an important clue to the diagnosis.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of bone tumors (2020 - blue book) 1:
- epithelioid and/or spindle cell morphology in the majority of the tumor
- no histological or molecular signs of leiomyosarcoma or synovial sarcoma
Additional desirable diagnostic criteria include the following 1:
- tumor location in the left atrium
- a polypoid form
- absence/minimal myxoid or fibrotic matrix
Clinical presentation
Clinical signs and symptoms are related to the left atrium and might include dyspnea, palpitations and symptoms of heart failure or non-specific constitutional symptoms such as fever and weight loss 1.
Complications
Cardiac undifferentiated pleomorphic sarcomas might cause the following complications 1-3:
- arrhythmias as atrial fibrillation, atrioventricular block or ventricular tachycardia
- embolic events
- heart failure
- pericardial effusion
- distant metastases
Pathology
Cardiac undifferentiated pleomorphic sarcomas are high-grade sarcomas consisting of pleomorphic spindled or epithelioid cells with no specific differentiation 1,3.
Etiology
The etiology of cardiac undifferentiated pleomorphic sarcomas is unknown 1.
Location
Cardiac undifferentiated pleomorphic sarcomas most often arise from the left atrium and less commonly from other cardiac chambers 1,2. The posterior or lateral left atrial wall are more frequently affected than the left atrial appendage or the mitral valve. Less commonly, they arise from the left atrial septum, fill the entire left atrial chamber, or rarely arise from multiple sites 1.
Macroscopic appearance
Macroscopically cardiac undifferentiated pleomorphic sarcomas are usually large at the time of diagnosis and have a polypoid or lobulated appearance that projects into the atrial cavity. Early in the disease process, they are usually characterized by very little involvement of the myocardium 1.
Microscopic appearance
Microscopically cardiac undifferentiated pleomorphic sarcomas display the following histological features 1:
- atypical pleomorphic spindle cells and epithelioid cells
- frequent mitoses
- nuclear pleomorphism
- commonly necrosis
- possible foci of chondroid or osseous matrix
- resemblance to intimal sarcoma
Immunophenotype
Immunohistochemistry might be positive for MDM2 1-3.
Radiographic features
Echocardiography
Echocardiography might show a polypoid mobile echogenic mass of the cardiac chambers 4,5.
CT
Cardiac CT might show a polypoid intracardiac mass.
MRI
Cardiac MRI might demonstrate an irregular or lobulated or polypoid mass 3-5.
Signal characteristics
- T1: isointense
- T2: hyperintense
- T1C+ (Gd): heterogeneous late enhancement
Radiology report
The radiological report should include a description of the following:
- form including base
- location, extent
- lesion mobility
- relation to other chambers and valves
- extension to adjacent structures
- pericardial effusion
Treatment and prognosis
Cardiac undifferentiated pleomorphic sarcomas are characterized by a very poor prognosis with a median survival of less than a year 1-4. Management is usually multidisciplinary and includes surgery, chemotherapy and possibly radiotherapy even though a clear role for the two latter treatment modalities has not been established yet 2.
Differential diagnosis
Conditions or tumors that might mimic the imaging appearance of cardiac undifferentiated pleomorphic sarcomas include 1: