Cardiac tumors are infrequent and most often secondary to a metastatic process. Primary cardiac tumors are usually benign, the most prevalent of them being cardiac myxoma.
Primary cardiac lymphoma (PCL) is a rare entity accounting for less than 2% of primary cardiac tumors: it lacks a univocal definition, and the evidence in literature derives almost exclusively from case reports [1,2,3,4,5,6,7,8,9,10,11,12,13]. Secondary cardiac involvement of a disseminated lymphoma is, on the other hand, quite common.
The diagnostic criteria for PCL have progressively broadened over time. The definition of PCL was initially reserved for a mass with exclusive involvement of the heart or pericardium, while at present, it can be made when the primary bulk of the lymphoma is localized in the heart or pericardium even if limited extracardiac lymphoma is present—mostly when the clinical manifestations are related primarily to cardiac dysfunction [2, 3].
PCL is typically a subtype of non-Hodgkin B cell lymphoma, most often diffuse large B cell lymphoma. The overexpression of both C-MYC and BCL2 without a chromosomal rearrangement (double expressor DLBCL), which can be seen in about 20% of DLBCL, carries a poor prognosis, which is even worse if there is a concomitant chromosomal rearrangement of the two genes (double hit-double-expressor DLBCL) [4, 5].
PCL is classically a disease that affects the right heart with a strong predilection for the right atrium: only a few cases of lymphomas with the main bulk at the level of the left sections are present in the literature. Pericardial effusion is often present.
Clinical manifestations of PCL are often vague, which accounts for the late diagnosis and poor prognosis of the disease: the most common symptom is dyspnea. Other clinical signs and symptoms depend largely on the localization of the tumor (e.g., superior vena cava syndrome in case of right heart involvement) and its infiltration of the myocardium or coronary arteries that can be responsible, respectively, for the onset of arrhythmias and angina. Almost half of the patients can experience symptoms of heart failure [6, 7].
Multimodality imaging is essential to determine the nature of a cardiac mass and can guide towards the diagnosis of PCL. Echocardiography is usually the first imaging step; cardiac CT and MRI offer further tissue characterization and anatomical information. In contrast, nuclear imaging is most useful in therapeutic management and to evaluate the response to chemotherapy.
Multimodality imaging can help in the characterization of a cardiac tumor: echocardiography is the first choice examination to identify the mass and evaluate its hemodynamic impact; CMR allows better soft-tissue characterization, high resolution, and multiplane images acquisition; CT provides morpho-structural information of the mass and coronary arteries imaging and is the method of choice when CMR is contraindicated. Large size (≥ 5 cm), irregular margins, pericardial effusion, and invasion of the free wall and/or the adjacent structures are features of malignancy. T1- and T2-weighted imaging (T1W, T2W) do not differentiate benign and malignant masses, while First Pass Perfusion (FPP) and LGE are more accurate [8,9,10]. Still, a definite diagnosis—ruling out other possible cardiac malignancies like angiosarcoma—can be obtained only through a bioptic exam, necessary to guide treatment strategies.
Six cycles of combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) treatment combined with six doses of rituximab given every 21 days is the current standard for diffuse large B cell lymphoma. Consolidation by radiotherapy to initial non-bulky sites has no proven benefit in patients treated with rituximab or not. Debulking surgery can be an option when the mass of the tumor is responsible for symptoms like refractory heart failure or superior vena cava syndrome [12, 13].
Myocardial infiltration of the lymphomatous mass potentially exposes to the risk of myocardial rupture during chemotherapy; the prevalence of this catastrophic event is unknown, but it is considered a significant threat, as it can occur spontaneously in patients with extensive myocardial involvement. Various case reports in the literature suggest dose reduction of initial chemotherapy using different protocols, with subsequent escalation to standard dosage to minimize this risk [14].
Individualized strategies are necessary and, once again, imaging techniques can guide towards the decision of a dose reduction balancing its benefits in preventing heart rupture with the possible downside of not obtaining an optimal response to treatment.
