| Abstract|| |
Primary rhabdomyosarcoma (RMS) of the heart is a rare malignant tumor which has poor prognosis and survival despite surgery and adjuvant chemotherapy. The preoperative diagnosis is often difficult in view of nonspecific clinicoradiological findings. This report describes a case of a 60-year-old woman who was clinically diagnosed as left atrial myxoma. A diagnosis of pleomorphic RMS was made on histopathology after excision. Our case discusses the clinicopathological features and treatment options of cardiac RMS emphasizing the fact that histopathology and immunohistochemistry are essential to confirm the diagnosis of such an aggressive malignant tumor.
Keywords: Cardiac sarcoma, myxoma, pleomorphic rhabdomyosarcoma
|How to cite this article:|
Aggarwal T, Goyal S, Zaheer S. Pleomorphic rhabdomyosarcoma of the left atrium mimicking myxoma. Indian J Pathol Microbiol 2016;59:379-81
| Introduction|| |
Primary tumors of the heart are rare with an incidence of 0.001–0.28%. Of these, 75% are benign and rest 25% are malignant. Metastatic tumors are 20–40 times more common than primary malignant tumors of the heart. Primary sarcomas are much more common than carcinomas.
Myxomas make up 50–70% of all primary benign tumors. The common sarcomas in adults include angiosarcoma (25%) followed by rhabdomyosarcoma (RMS), pleomorphic sarcoma, and leiomyosarcoma in the decreasing order of incidence. RMS accounts for 20% of all primary sarcomas of the heart. It localizes mainly in the left atrium followed by right ventricle., It is an aggressive tumor of cardiac muscle origin which diffusely infiltrates the myocardium and occasionally forms a polypoidal mass. By the time patients present with cardiac symptoms, tumor has already metastasized to other sites. Clinically and radiologically, RMS is often misdiagnosed as pseudoinflammatory tumor and myxoma. However, few articles have suggested the potential role of computed tomography (CT) in differentiation of atrial myxoma from intracardiac malignant tumors such as RMS., Although RMS has been commonly reported in soft tissues, very few cases of adult cardiac RMS have been reported from India and South Asia.,
| Case Report|| |
We report a case of a 60-year-old woman who presented with a complaint of shortness of breath on moderate exertion which was gradual in onset. There was history of intermittent low-grade fever for the last 1 year. She had previously been well, and in particular, there was no history of rheumatic fever, ischemic heart disease, or pulmonary disease. On clinical examination, her vital signs were within normal limits. On palpation, apical impulse was felt in the fifth intercostal space. Epigastric pulsation was present with Grade 3 left parasternal heave. The left second intercostal area was dull on percussion. Auscultatory findings revealed mid-diastolic murmur in the mitral area with Grade 3 parasystolic murmur in the tricuspid area. S1 and S2 were normal with loud P2. Complete hemogram, biochemical, and urine examination findings were normal. Chest X-ray showed centrally placed trachea, enlarged left atrium and right atrium with double atrial shadow, prominent pulmonary artery with plethoric lung fields, and prominent vascular markings. Right-sided pleural effusion was present with unremarkable lung parenchyma. Pleural fluid was sent for cytological examination which showed predominantly lymphocytes along with few neutrophils and reactive mesothelial cells.
Contrast-enhanced CT (CECT) of the chest revealed a large lobulated hypodense lesion in the left atrium extending into the right lower lobe pulmonary veins with bilateral pleural effusion [Figure 1]. The mass appeared to be attached to the interatrial septum. Coronary angiography showed normal coronaries.
|Figure 1: (a) Contrast-enhanced computed tomography of the chest revealed a large lobulated hypodense mass lesion in the left atrium extending into and dilating the right inferior pulmonary vein (arrow). Note is also made of right side pleural effusion. (b) Cut surface of tumor shows well-circumscribed gray-white mass with areas of hemorrhage, necrosis and myxoid change|
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Echocardiogram was done which revealed a large, nonpedunculated, echogenic mass in the left atrium measuring 10.5 cm × 7.7 cm which was attached to the interatrial septum. Based on clinical and radiological findings, a provisional diagnosis of left atrial myxoma was made and surgical removal of was recommended.
Peroperatively, right atrium, right ventricle, and left atrium were enlarged. A sessile tumor mass was seen in the left atrium which was superficially attached to the interatrial septum and infiltrating into the right inferior pulmonary vein. Mitral valve was normal. The tumor did not infiltrate the underlying endocardium. The mass was removed via median sternotomy on the cardiopulmonary bypass. Mild pericardial effusion was noted without any adhesion. There was no evidence residual tumor in the left atrium with tumor sent for histopathological examination. We received two globular grey-white encapsulated soft-tissue pieces measuring 6.3 cm × 3.5 cm × 1.8 cm and 4.5 cm × 4 cm × 2 cm, respectively. Cut surface was gray-white, homogeneous, soft with myxoid areas and focal hemorrhagic areas [Figure 1]. Microscopic examination showed a well-circumscribed spindle cell tumor comprising hypercellular and hypocellular myxoid areas [Figure 2]. Tumor cells were arranged in intersecting fascicles, bundles, and at places in storiform pattern [Figure 2]. Areas in which tumor cells are arranged in sheets and lobules were also seen. The cells were round to oval with moderate to abundant eosinophilic cytoplasm, hyperchromatic nucleus, and inconspicuous nucleoli. Some of these cells have clear to vacuolated cytoplasm [Figure 3]. On extensive search, a few multinucleated giant cells and rhabdomyoblasts (strap cells) were seen [Figure 3]. Cross striations were evident in a few strap cells by phosphotungstic alum hematoxylin. Atypical mitoses were seen (5–6/HPF). In areas of storiform pattern, cells have scant amount of cytoplasm and have elongated nuclei with pointed ends. Focal areas of necrosis and hemorrhage were also seen. On immunohistochemistry, tumor cells showed cytoplasmic positivity for vimentin and desmin and negative for smooth muscle actin (SMA), CD34, S-100, factor VIII, CD99, and WT-1 [Figure 4]. Based on morphological and immunohistochemical findings, a diagnosis of pleomorphic RMS, the left atrium, was made.
|Figure 2: (a) Section shows hypercellular areas with tumor cells arranged in storiform pattern. (b) Photomicrograph shows hypocellular myxoid areas (H and E, ×200)|
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|Figure 3: (a) Section shows elongated tadpole and strap cells “rhabdomyoblasts” (arrow). (b) Photomicrograph shows round to oval tumor cells having moderate to abundant eosinophilic cytoplasm, hyperchromatic nuclei, and inconspicuous nucleoli. Some of the cells have vacuolated cytoplasm. Numerous atypical mitoses are seen (arrow) (H and E, ×400)|
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|Figure 4: (a) Immunohistochemistry (a) tumor cells showing cytoplasmic positivity for desmin. (b) Tumor cells are negative for smooth muscle actin (Immunostain, ×400)|
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Postoperative echocardiography showed left ventricular ejection fraction of 60% without any significant dysfunction of the cardiac valves and resolution of pericardial effusion. Left atrium did not show any residual tumor. However, a part of tumor was adherent to the inferior pulmonary vein which was not dissectible in view of injury. Postoperative period was uneventful, and the patient was discharged 10 days after the surgery. The patient has been kept on follow-up with echocardiography, X-ray, and CECT. The patient is symptom-free after surgery.
| Discussion|| |
Malignant neoplasms constitute about 25% of all primary cardiac tumors. Of these, metastatic carcinomas are much more common than primary sarcomas of the heart. Most common primary sarcoma is angiosarcoma followed by RMS., Cardiac RMS is an aggressive tumor with high mortality. It has been reported in all age groups with equal male and female preponderance. Around 65 cases of primary cardiac RMS in adults have been reported till now. On review of the literature, the decreasing order of site of involvement was left atrium (55%) followed by left ventricle (15.7%), right ventricle (15.7%), and right atrium (13%). Symptoms of cardiac sarcomas depend on the degree and exact site of involvement and may include valvular obstruction, arrhythmias, heart failure, pericardium effusion, systemic embolization, and systemic symptoms. Till now, <5 cases of primary cardiac RMS in adults have been reported from South Asian population.,
Preoperative differentiation between benign lesion (thrombus/atrial myxoma) and sarcoma is clinically important but diagnostically challenging due to lack of specific radiological findings on echocardiography. However, with recent advances in technology, a few authors have suggested a role of transthoracic and transesophageal echocardiography for the evaluation of cardiac tumors, the reported sensitivity of echocardiography is 90–95% in differentiating between thrombi, cardiac benign and malignant tumors, making it a valuable preoperative investigation.,
Morphologically, the differential diagnoses of round to elongated pleomorphic cells with eosinophilic cytoplasm include high-grade sarcomas such as leiomyosarcoma, angiosarcoma, malignant fibrous histiocytoma, and pleomorphic undifferentiated sarcoma apart from RMS. Presence of strap cells “rhabdomyoblasts” with dense eosinophilic cytoplasm and immunopositivity for desmin favored a diagnosis of RMS. Negative staining for SMA, CD34, and factor VIII excluded the possibility of leiomyosarcoma and angiosarcoma.
The proposed treatment of choice as discussed in various case reports is surgical resection. Owing to the limited number of reported cases and lack of randomized studies, there are no standardized guidelines regarding the role of adjuvant chemotherapy in RMS. It is believed that adjuvant chemotherapy slightly improves patient survival. A survival rate of <15 months has been reported with surgery as the only treatment modality. Although longer median survival times have been reported in a few patients who underwent complete surgical resection and orthotopic heart transplantation, recurrence and death have been reported in majority of these. On literature review, most of the patients (72%) had died due to cardiac complications such as cardiogenic shock, complex arrhythmias, conduction disturbances, pericarditis, and embolism. Other rare causes of death included metastasis to liver (5.5%), brain (5.5%), and lungs (5.5%). In a study done on 75 cases, the survival rate had been found to be more favorable for patients with tumors located on the left side of the heart, without necrosis, with a low mitotic count, and without metastasis at the time of diagnosis. It was found that although the prognosis is dismal in patients with cardiac sarcomas, histologic grading is useful in predicting outcome.
| Conclusion|| |
Cardiac RMS is a rare and aggressive malignant tumor of the heart which is difficult to diagnose preoperatively. Excision is indicated to confirm the diagnosis provide palliative relief and improve short-term survival. Despite surgery, the survival is not more than 15 months due to high chances of cardiac complications and metastases. Our case discusses the diagnostic approach, clinicopathological features, and prognosis of this rare cardiac tumor in view of its high mortality.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Surbhi Goyal
Department of Pathology, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]