Cardiac undifferentiated pleomorphic sarcoma

Last revised by Joachim Feger on 26 Dec 2021

Cardiac undifferentiated pleomorphic sarcomas are highly malignant mesenchymal tumors of the heart.

Terms that are no longer recommended for use include ‘intimal sarcoma’, ‘undifferentiated sarcoma’ and ‘undifferentiated spindle cell sarcoma’ 1.

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.

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 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 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.

Cardiac undifferentiated pleomorphic sarcomas might cause the following complications 1-3:

Cardiac undifferentiated pleomorphic sarcomas are high-grade sarcomas consisting of pleomorphic spindled or epithelioid cells with no specific differentiation 1,3.

The etiology of cardiac undifferentiated pleomorphic sarcomas is unknown 1.

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.

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.

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

Immunohistochemistry might be positive for MDM2 1-3.

Echocardiography might show a polypoid mobile echogenic mass of the cardiac chambers 4,5.

Cardiac CT might show a polypoid intracardiac mass.

Cardiac MRI might demonstrate an irregular or lobulated or polypoid mass 3-5.

  • T1: isointense
  • T2: hyperintense
  • T1C+ (Gd): heterogeneous late enhancement

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

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.

Conditions or tumors that might mimic the imaging appearance of cardiac undifferentiated pleomorphic sarcomas include 1:

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