Primary cardiac myxofibrosarcoma with osteoid differentiation mimicking a left atrial myxoma: A rare entity

Abstract

Cardiac myxofibrosarcoma (MFS) is an uncommon entity. It is among the most challenging conditions to diagnose due to its rarity, high variability, and non-specific findings. These tumors often simulate left atrial myxoma or mitral stenosis at clinical presentation. Although, the definitive diagnosis of cardiac tumors depends on histopathological examination, various imaging techniques are also useful to study tumor characteristics to plan an appropriate treatment strategy. Here we highlight a case of primary cardiac MFS of left atrium (LA) showing areas of transition to undifferentiated pleomorphic sarcoma (UPS) with bone or osteoid formation, which is extremely rare and not well described. <Learning objective: Primary cardiac myxofibrosarcoma (MFS) is a rare and aggressive cardiac tumor. It is often confused with benign myxoma, leading to a delay in initiation of treatment. This delay can often lead to poor clinical outcomes. Our study will guide clinicians in early diagnosis, treatment, and counseling of patients with this rare entity. Echocardiography, together with magnetic resonance imaging, histology, and immunohistochemistry are essential in the diagnosis of MFS.>.

Keywords: Left atrial myxoma; Myxofibrosarcoma; Undifferentiated pleomorphic sarcoma.

Fig. 1

(a) Transthoracic echocardiography. Parasternal long-axis view showing a large tumor in the left atrium (LA) (arrow) with calcification and prolapse. (b) Transesophageal echocardiography showing multi-lobulated mass (white arrows) arising from posterior wall of LA with areas of cystic degeneration (black arrow).

Fig. 2

(a) Intraoperative image showing a large pearly white, hard mass arising from the posterior wall of left atrium (black arrow). (b) On excision, firm to hard, grayish white, nodular masses with cut surfaces having myxoid appearance interspersed with areas of dense calcification.

Fig. 3

Histopathology of tumor. Hematoxylin and eosin-stained sections of tumor showing: (a) Nodular pattern with arborizing blood vessels (black arrow) and myxoid stroma (white arrow). (b) Hypercellular areas with pleomorphic spindle cells (black arrow) and epithelioid cells (white arrow). (c) Hypocellular areas with few scattered spindle cells within a predominant myxoid (black arrow) and fibrous stroma (red arrow). (d) Scattered areas of woven bone (black arrows) and osteoid deposition (red arrow).