Discussion
Myxoma is the most common type of tumour among all primary cardiac neoplasms [1]. Usually, they originate from the oval fossa with a growth directed towards the left atrial cavity [3]. Common symptoms are related to embolic events due to myxoma fragments embolization and syncope episodes due to diastolic obstruction of the mitral valve [1].
Cardiac lymphomas are instead rare, amounting to only 0.6% of all cardiac tumours. Although several subtypes of lymphomas may arise in the heart, the most common is diffuse large B-cell lymphoma not otherwise specified (DLBCL-NOS), usually associated with an aggressive biologic behaviour [5-7].
On the other side, the most frequent lymphoproliferative disease associated with cardiac myxoma is fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL), with 16 cases reported so far [8].
FA-DLBCL is a recently recognized entity [9], included within the spectrum of diffuse large B-cell lymphomas associated with chronic inflammation and has highly distinctive features: it arises in fibrinous material covering or contained in sites of chronic inflammation (most commonly within the cardio-vascular system), neither forming a mass nor producing specific symptoms [9, 10]. Typically, the diagnosis is incidental, during histologic examination.
FA-DLBCL is invariably EBV-positive.
It is therefore likely that most of the previous reported cases of lymphomas arising in association to cardiac myxomas would be re-classified into FA-DLBCL according to the current WHO classification, due to the concomitant [9] positivity for EBV [10-18] and for the typical localization within the fibrinous material covering the myxoma [19, 20].
Most importantly, despite aggressive histologic features (large cell morphology, high proliferation index), FA-DLBCL is a localized disease with an indolent behaviour and a favourable outcome even with surgical excision alone. The rare event of relapse and the associated risk of local invasion [3, 9, 21], however, reinforces the need for a complete surgical excision.
Our case report suggests that cardiac surgeons must be aware that even apparently benign cardiac masses can conceal malignant lesions, adopting an attitude of presumption of “malignity until proven otherwise”, that should prompt always an accurate and radical excision of the mass.
The recognition of a macroscopic unusual appearance of the lesion is of paramount importance, as
all the reported cases of lymphoid proliferation arose within a cardiac myxoma showed a partial or global gelatinous aspect of the neoplasm (especially in its peripheral areas) (Tab 1).
The rarity of this disorder is an obstacle to prospective studies. Endocavitary masses with the peculiar macroscopic characteristics we have described could indicate a high probability of lymphocytic infiltration in the context of myxomatous masses. In this case, a specific, integrated diagnostic and therapeutic pathway should be followed, including: wide and radical resection and possibly a bone marrow specimen (easily collectable during surgery from the sternal bone), to ensure a fast staging if the lesion would be proven malignant.