Secondary cardiac neoplasms or cardiac metastasis/es refer to a secondary malignant tumour of the heart, arising by lymphatic or haematogenous spread of a primary neoplasm 3,5.
Overall cardiac malignancy is an infrequent finding. Metastatic spread is much more common than primary cardiac malignancy, with a factor approximating 30 to 1. Series of autopsia cadaverum in patients with widespread disease burden revealed cardiac involvement in 12-25% of cases 3. Larger series (n=662) have demonstrated sole cardiac involvement by a metastasising malignancy in no more than 1,5 % of cases 5.
Virtually any primary malignancy may metastasise to the heart, however, the most often encountered primaries comprise:
- lung, breast, kidney, thyroid carcinomas and malignant melanomas
- lymphomyeloproliferative types lymphoma and leukaemia
As such, incidence of cardiac involvement reflects a combination of:
- aggressiveness of the individual malignancy
- frequency in which the underlying malignancy occurs 5
Often missed during initial diagnostic work-up for primary diagnosis, secondary cardiac involvement may not be detected for many years. Not infrequently it is not diagnosed clinically at all and found at autopsy.
Potential presenting signs and symptoms may greatly vary, influenced by the location of tumour deposit(s) 3,5:
- dyspnoea and congestive heart failure, hypotension:
- malignant pericardial effusion
- infarction, arrhythmias, hypoxia and hypotension:
- affection of myocardium or conductive system
- intracavitary mass
- valvular implants
In most cases multiple metastatic tumour deposits are encountered. Locations and their frequency are as follows 3:
- right cavities, roughly one third of cases
- left cavities, another third
- bilateral involvement in the remaining cases
Pathways of spreading may occur 3,5:
- predominantly lymphatic via mediastinal nodes and invasion of epicardial and pericardial lymphatics
- predominantly haematogenous
- superficial myocardial involvement
- intraluminal extension via the inferior vena cava and right atrium
- extension via the pulmonary vein
Typical features include:
- diffuse studding and thickening of the pericardium
- nodular, white-tan infiltrations on cut section
- associated desmoplastic reaction resulting in pericarditis constrictiva (frequently caused by directly extending lung malignancy)
A singular mass, endocardial involvement or intracavitary tumour is less commonly encountered 3,5.
Often resembles morphological features of the causative malignancy.
In cases of unknown primary or long interval between primary malignancy and diagnosis of cardiac involvement, immunohistochemical analysis may be necessary.
Encountering a high-grade, undifferentiated tumour may necessitate extensive use of immunohistochemical stains, a preliminary panel of which should include keratinic, melanocytic and lymphoid markers (confer list of most common primaries) 3,5.
Masses are rarely amenable to biopsy. Knowledge of the often characteristic imaging features is a prerequisite for providing a meaningful list of differential diagnosis.
Findings are non-specific on chest x-ray, but may include:
- cardiomegaly (e.g. indicating pericardial effusion and/or cardiac congestion)
- gross mediastinal lymphadenopathy
Comparison with previous films is important.
Transthoracic echocardiography (TTE)
Very often the initial imaging method of choice, albeit both operator-dependent and influenced by patient-related factors. The limited field-of-view may preclude complete assessment of an invading mass, but depicting pericardial effusion is usually straightforward. It may also allow for detection of ventricular masses.
Transoesophageal ultrasound (TOE)
TOE usually offers a more detailed assessment, allowing for detection of sub-centimetre masses or tumours located within the atria or near the valves. The lack of confident tissue characterisation, however, often necessitates the use of cross-sectional imaging.
General features comprise:
- multiple masses or nodules with heterogeneous enhancement pattern, best diagnostic clue
- diffuse infiltration may also occur
- epicardial and pericardial masses with associated effusion, usually complex
- changes in contour of the cardiac chambers and/or septum interventriculare
The latter finding may alert to the need for pericardiocentesis.
Cardiac MR (ECG-gated MR) is the imaging modality of choice due to:
- high temporal resolution (30–50 ms)
- excellent soft-tissue contrast
Imaging features are as listed above. Typical characteristics of masses are:
- T1: hypointense
- T2: hyperintense
- almost always significant contrast enhancement post gadolinium injection
In addition, malignant melanoma deposits typically show high T1 signal caused by paramagnetic properties of melanin, thus allowing for a specific diagnosis of the primary malignancy 7,13, obviating the need for biopsy.
As stated above. May depict calcifications. Masses typically show soft-tissue attenuation on CT 7.
Most frequent CT features of pericardial metastases include pericardial effusion, prepericardial lymph nodes, and pericardial thickening, enhancement, and nodules in order of decreasing frequency 2.
Distribution is as follows 1:
- pericardium is by far the most commonly affected site
- myocardium can be involved through direct tumor extension from the pericardium. However, malignant melanoma may result in diffuse myocardial involvement through hematogenous spread
- only about 5% of cardiac metastases are endocardial/intracavitary lesions
18F-FDG PET/CT with state-of-the-art CT may aid in differentiation between benign and malignant cardiac tumours.
Likely the best present imaging modality to assess the widespread nature of the causative primary malignancy 4.
Likely the imaging reference of the near feature, combining advantages of both modalities, i.e. excellent soft tissue contrast and molecular imaging 14.
Treatment and prognosis
As mostly encountered in widespread disease, treatment is often palliative and addresses the underlying malignancy. Pericardiocentesis may be indicated to relieve symptoms caused by effusion (see also imaging features indicating cardiac tamponade). Although a rare finding, single nodules may be resectable 3.
The distinction between primary and secondary cardiac neoplasms is, usually, easily made on clinical grounds since almost all cardiac metastases manifest in patients with known non-cardiac primary malignant neoplasms 1,3,5.
It is important to keep in mind that, although usually part of widespread metastatic disease, metastatic cancer may present as malignant pericardial effusion 5.
In cases of doubt, or on encountering findings suggestive of malignant cardiac disease without known primary malignancy, general differential diagnostic considerations may include
- other causes of pericardial effusion
- anatomic variants
- thrombi and pseudothrombi (flow-related changes)
- primary cardiac neoplasms (albeit much less common)
A walk through rarity section offers illustrative examples regarding the ratio of primary and secondary cardiac neoplasm, e.g.
- multiple cardiac metastases from a non-functioning pancreatic neuroendocrine tumour (pNET) 8
- squamous cell carcinoma of the bladder presenting as a metastatic right ventricular mass 9
- metastasis of a pulmonary undifferentiated pleomorphic sarcoma to the right ventricle 10
- extension of adrenocortical carcinoma into the right atrium 11
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