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.