Most heart tumors are metastatic, with an incidence rate of more than 20–40 times than the primary cardiac tumors [1]. Primary cardiac tumors are rare, with a prevalence of autopsy being reported to be 0.001–0.030% [2]. Among all the primary tumors, the malignant one’s account for about 25% [4]. About 95% of primary cardiac malignancies are sarcomas and osteosarcomas, and the latter accounts for less than 10% [5]. In a literature study, 45 papers concerning primary cardiac osteosarcoma were included, and a total of 53 patients were reported [6]. Given its rare occurrence, there are no standard guidelines on its etiology, pathogenesis, and treatments.
The clinical symptoms of primary cardiac osteosarcoma mainly depend on the size and anatomical location of the tumor [7]. The common symptoms include dyspnea, chest pain and syncope, mainly related to heart failure and obstruction [3]. Fever was the main complaint of the current patient when he was admitted to our hospital, characterized by persistent high fever. There was merely one reported case of fever during the disease [8], which was attributed to upper respiratory tract infection, and the temperature returned to normal when he was admitted to our hospital. We hypothesized that the current patient might be complicated with infective endocarditis. However, as the patient had been treated with antibiotics many times before admission, no bacteria were detected by blood culture. Importantly, this reminds us that the long-term fever of unknown origin or infective endocarditis can also be one of the symptoms of primary cardiac osteosarcoma, which has never been reported before.
In contrast to the metastatic ones, a majority of the primary cardiac osteosarcomas most commonly involve the LA[9]. However, only one patient with simultaneous left atrial and ventricular involvement has been reported [10]. The difference is that in our case, the two tumors in the cardiac cavity are anatomically independent of each other, indicating the double primary malignancies. The similar clinical symptoms and anatomic location lead to the confusion between primary cardiac osteosarcoma and atrial myxoma; however, some characteristics are helpful to distinguish them [11, 12], such as myxomas tend to have a short and extensive base attached to adjacent sites, pedicled, soft, and often have some hemorrhagic and necrotic areas. Osteosarcoma generally originates from the non-septal atrial wall and often predisposes to invading the pulmonary vein.
Because primary cardiac osteosarcoma is exceptionally rare, there are few studies reported on its pathogenesis. Terje Forslund [13] proposed that some genes may regulate the disease, such as aberrant PI3K-Akt-NFkappaB pathway, and tbhs3 and erbB2 proteins overexpression. However, the death of the patient in this report did not allow any further tests. Based on this study, we plan to conduct whole gene sequencing for the current patient to further clarify the potential pathogenesis of the disease.
Osteosarcoma has a high degree of malignancy, and recurrence and metastasis are its basic characteristics [14], leading to the low survival rate of patients. The average survival time of osteosarcoma patients ranged from 3 months to 1 year [15]. Our patient had a recurrence of left ventricular tumor 3 months after the operation and is currently receiving chemotherapy.
Given the lower incidence of osteosarcoma in the LA and LV, there is no standard treatment guidelines. Complete surgical resection is considered to be the optimal therapy for the tumor [16]. Due to the low tolerance of myocardium to chemoradiotherapy, the role of chemoradiotherapy is controversial [9]. Given the previously reported case [13], a future procedure can be scheduled to detect some abnormal gene expression or molecular pathway in these patients, to develop some prospective targeted therapies.
We report a case of primary osteosarcoma in the LA and LV, and the patient had undergone complete tumor resection, and then received periodic chemotherapy owing to postoperative recurrence. This is the first case complaining of long-term fever as the main symptom on admission. The second case reported atrial and ventricular involvement simultaneously, enriching our understanding of the disease. Next, we intended to use tissue samples of the patient for gene detection to seek potential targeted therapy and provide new options for treating the disease.
In short, when confronted with difficult diseases, especially some rare conditions, we should pay attention to the unusual clinical manifestations. We should also focus on the correlations among clinical, pathological, and imaging evidences.