Cardiac leiomyosarcomas are malignant smooth muscle tumours of the heart.

Epidemiology

Cardiac leiomyosarcomas are rare primary malignant tumours of the heart accounting for less than one-fifth of cardiac sarcomas. They have been found in a wide age range from 6 months to 86 years with a mean age of 48 years and no gender predilection ^1,2.

Diagnosis

The diagnosis is based on the histological and immunohistochemical features ¹.

Clinical presentation

Clinical signs and symptoms depend on the tumour location and might include dyspnoea, cough, haemoptysis, palpitations, atrial fibrillation or peripheral oedema, pleural effusion and ascites as well as non-specific symptoms like fatigue, malaise, fever or weight loss ^1,2.

Complications

Cardiac leiomyosarcomas might cause the following ^3,4:

• arrhythmias as atrial fibrillation, atrioventricular block or ventricular tachycardia

• embolic events

• heart failure

• pericardial effusion

• valvular obstruction

Pathology

Cardiac leiomyosarcomas are malignant mesenchymal tumours arising in the cardiac chambers that might be intracavitary or infiltrating. Rarely they might have a stalk ^1,2.

Location

Cardiac leiomyosarcomas most frequently arise from the left atrial free wall and less commonly from the right atrium or the ventricle and rarely from the interatrial septum ^1,2.

Macroscopic appearance

Macroscopically, cardiac leiomyosarcomas have are multilobular nodular or polypoid, homogeneous sometimes whorled appearance with a white to tannish colour and a firm consistency and variably areas of necrosis ^1,2.

Microscopic appearance

Microscopically, cardiac leiomyosarcomas are characterised by the following histological features ^1,2:

• intersecting fascicles of spindle-shaped or epithelioid cells

• plump nuclei

• moderate to abundant pale to bright eosinophilic cytoplasm

• sometimes storiform or palisading patterns

• mitosis readily seen

• variably myxoid stroma

• frequent necrosis in larger tumours

Immunophenotype

On immunohistochemistry cardiac leiomyosarcomas usually express smooth muscle actin and desmin ¹.

Radiographic features

Differentiation of cardiac leiomyosarcomas from other cardiac tumours is difficult. An associated pericardial effusion, a broad base and an immobile lesion point towards malignancy ³.

Ultrasound

Echocardiography

Echocardiography might show an echogenic mass of the cardiac chambers ³.

CT

Cardiac leiomyosarcomas can be easily visualised with cardiac CT ².

MRI

Cardiac MRI can detect tumours with high sensitivity and characterise the location and extent of the lesion ^3-5.

Signal characteristics

• T1: isointense

• T2: hyperintense

• T1C+ (Gd): heterogeneous early and late enhancement

Radiology report

The radiological report should include a description of the following:

• type, location, extent and

• lesion mobility

• relation to other chambers and valves

• extension to adjacent structures

• pericardial effusion

Treatment and prognosis

Cardiac leiomyosarcomas are aggressive neoplasms. The mainstay in management consists of surgical excision with adjuvant chemotherapy or radiotherapy posing an uncertain asset. Local recurrences and distant metastasis are common with 5-year survival rates of approximately 25%. and a high mortality rate ^1,2.

Differential diagnosis

Condition or tumours that might mimic the imaging appearance of cardiac leiomyosarcomas include ^1-3:

• cardiac myxoma

• cardiac undifferentiated pleomorphic sarcoma

• cardiac rhabdomyosarcoma

• cardiac angiosarcoma

• cardiac thrombus