CASE REPORT
Preoperative Assessment of Thymoma Evaluation of Mediastinal Arterial Anatomy by Cardiac Multidetector Computed Tomography Daniele Andreini, MD,* Gianluca Pontone, MD,* Luca Dainese, MD,w Alberto Formenti, MD,* Saima Mushtaq, MD,* Antioco Cappai, MD,w Mauro Pepi, MD,* Giovanni Ballerini, MD,* and Paolo Biglioli, MDw
Abstract: We describe the clinical case of a thymoma, surgically removed after diagnosis, staging, and preoperative assessment performed by means of cardiac electrocardiogram-gated multidetector computed tomography. This technique allowed a very accurate assessment of the mass, proving superior to conventional computed tomography thanks to the possibility of identifying the relationships of the mass with the mediastinal structures, including the large vessels and coronary arteries. It also established the origin of the arterial vascularization from a tributary branch of the left internal mammary artery, visualizing the pathway and the relationship of the vessel with the mass and the point where it is penetrated. Finally, we analyzed the anatomy and patency of the coronary arteries, essential data in this patient with a high risk of coronary artery disease.
a complete preoperative assessment of a paracardiac mediastinal mass, investigating its vascularization and relationships with the adjacent cardiovascular structures and studying the patency of the patient’s coronary circulation.4–6
CASE REPORT
T
A 69-year-old male patient with hypertension and a family history of ischemic heart disease was admitted to our Center in March 2007 with a diagnosis of an anterior mediastinal mass, detected by chest x-ray. On admittance, the patient’s only symptoms were sporadic episodes of palpitations. The objective examination and the blood tests were all normal. The electrocardiogram showed a regular sinus rhythm and grade I atrioventricular block. A chest x-ray confirmed the presence of a circumscribed mass projecting over the left anterior mediastinum, with no other abnormality (Fig. 1). A cycle ergometer stress test did not reveal a reduced coronary reserve. A transthoracic echocardiogram showed the presence of a mass with a homogeneous echostructure and defined margins, measuring 71 60 mm. The mass was visualized from the second/third intercostal spaces. From the standard views it was not easy to define spatial relationships
From the *Institute of Cardiology; and wDepartment of Cardiac and Vascular Surgery, Centro Cardiologico Monzino, IRCCS, University of Milan, Milan, Italy. No conflict of interest exists. Authors assure that the data are original and have not been published previously nor are in consideration for publication elsewhere at the present time. All Authors have reviewed and approved the conclusions reached in the manuscript. Reprints: Daniele Andreini, MD, Centro Cardiologico Monzino, Institute of Cardiology, Via C. Parea 4, 20138 Milan, Italy (e-mail:
[email protected]). Copyright r 2009 by Lippincott Williams & Wilkins
FIGURE 1. Chest x-ray (A) shows the presence of a circumscribed, marked projection of the left mediastinal profile with no evident pleuroparenchymal alterations. Transthoracic echocardiography (B, C): an off-axis parasternal short-axis view (B) shows the presence of a mass with delimited borders (head arrows); apical 4 chambers view (C) shows lack of spatial continuity of the mass with heart chambers. LA indicates left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.
Key Words: multidetector CT, thymoma, coronary arteries
(J Thorac Imaging 2009;24:31–33)
hymomas are the most frequent primary tumors of the thymus. The majority of thymomas are encapsulated and usually display a benign behavior, whereas in some cases they are locally invasive or even lead to distant metastases.1 The most frequent clinical presentation is an anterior mediastinal mass in an asymptomatic patient, identified as a result of a chest x-ray or a chest computed tomography (CT) scan. CT is the method of choice for characterization of the mass, for investigating the presence of any invasion of the adjacent structures, pleural implants, lymph node, or extramediastinal metastases and for the differential diagnosis with other mediastinal tumors.2,3 Over the last few years, thanks to its high spatial and temporal resolution, multidetector electrocardiogram-gated cardiac CT has proved to be a highly accurate method in identifying the presence of major stenoses in the coronary epicardial arteries. Cardiac CT is therefore able to provide
J Thorac Imaging
Volume 24, Number 1, February 2009
31
Andreini et al
FIGURE 2. Volume rendering computed tomography imaging (A, B) shows the thymic mass and its relationships with the surrounding anatomic structures. A number of arterial branches can be seen, arising from the left internal mammary artery and penetrating the mass, vascularizing it (B, arrow). Multiplanar reconstructions (C, D) show the anatomic relationships of the lesion excluding significant compression or infiltration of the mediastinal structures and the presence of calcifications and irregular intralesional arterial enhancement. The presence of a thin fat plane, separating the mass from the pulmonary artery, suggests lack of infiltration of this vessel (arrow). A indicates aorta; LAD, left anterior descending artery; LIMA, left internal mammary artery; LMA, left main artery; PA, pulmonary artery; RCA, right coronary artery; T, thymoma.
J Thorac Imaging
Volume 24, Number 1, February 2009
with the heart even though apparently it was capsulated without interference with heart chambers (Fig. 1). Doppler examination showed no gradients at the level of the pulmonary valve and right ventricle outflow. A retrospective gating cardiac CT with dedicated field of view for the heart (VCT, General Electric, 64-slice, with 64 0.625 mm collimation, 330 ms gantry rotation time, 120 kV tube voltage, patient preparation by 10 mg metoprolol intravenously) showed the presence of a voluminous oval-shaped, solid expansive process, with nonhomogeneous density, clear margins, and maximum dimensions of 77 71 mm in the left anterior mediastinal area. This lesion had a number of linear calcifications both inside and around the edges and significant contrast medium arterial enhancement. An arterial tributary branch within the expansive process starting from the middle third of the left internal mammary artery was clearly visualized. This vessel appeared to penetrate the process where it breaks up into small tributary branches. The lesion appeared to be well circumscribed with respect to the pericardium and the common trunk of the pulmonary artery, which seems to be slightly compressed by the mass but not infiltrated (Fig. 2). Overall appearance was indicative of a thymoma. Evaluation of coronary arteries showed absence of significant stenoses of the main coronary epicardial arteries which presented only 2 moderate stenoses in the midsection of the left anterior descending artery and the proximal section of the left circumflex artery (Fig. 3). A retroreconstruction with enlarged field of view allowed to exclude pleural or transdiaphragmatic spread of the mass. In view of these findings the mass was surgically removed by means of median sternotomy and pericardiectomy after clamping of the vascular pedicle starting from the left internal mammary artery. The mass was rounded, approximately 6 cm in diameter, reddish-brown in color, elastic, smooth, and highly vascularized. Macroscopic analysis revealed an oval-shaped, grayish tumor, measuring 7 5 cm, partly calcified, and hemorrhagic. The histologic diagnosis was a thymoma locally infiltrating the peritumoral mediastinal adipose tissue and capsule. The postoperative echocardiogram was normal. The patient was discharged on the seventh postoperative day in good clinical condition. The predischarge chest x-ray showed only pleural blurring of the left basal plane.
FIGURE 3. Coronary arterial tree. Volume rendering reconstructions (A–C) and multiplanar reconstructions (D–F) show the main coronary epicardial vessels, revealing the presence of 2 calcified stenoses of moderate degree at the level of the proximal section of the LAD and the midsection of the LCX (arrows). LAD indicates left anterior descending artery; LCX, left circumflex artery; LMA, left main artery; PDA, posterior descending artery; PLA, posterior lateral artery; RCA, right coronary artery.
32
r
2009 Lippincott Williams & Wilkins
J Thorac Imaging
Volume 24, Number 1, February 2009
DISCUSSION The main findings of this report are that 64-slice CT allowed a single comprehensive examination that provided accurate preoperative evaluation of a large thymoma, without motion artifacts, including coronary artery evaluation. Thymomas are the most frequent primary tumors of the thymus and, together with cancer of the thymus, account for around 15% of all mediastinal masses. Since its introduction into clinical practice, CT has represented the method of choice for the study of mediastinal masses, allowing differential diagnosis and locoregional staging. As far as thymomas are concerned, CT is useful in evaluating any invasion of the adjacent mediastinal structures, particularly the vascular structures such as the common trunk of the pulmonary artery. Thanks to its high spatial and temporal resolution, the latest generation of spiral multidetector CT scanners allows an accurate cardiac and vascular structures study, including the evaluation of coronary arteries. A complete preoperative assessment was therefore possible in this patient with this method. First, cardiac CT identified the relationships of the mass with the adjacent mediastinal structures,2 including the large arterial vessels (the common trunk of the pulmonary artery was slightly compressed without infiltration) and the coronary arteries (the left main artery and the proximalmiddle section of the left anterior descending artery where close, but not strictly adjacent to the lower portion of the mass) (Fig. 2). As these structures are affected by the systolic-diastolic motions of the heart, it would have been even more difficult (pulmonary artery) or even impossible (in the case of the coronary arteries) to evaluate their relationships with the mass by means of conventional CT.
r
2009 Lippincott Williams & Wilkins
Preoperative Assessment Of Thymoma
The examination also showed in details the origin of the arterial vascularization of the mass from a tributary branch of the left internal mammary artery, the relationships of the vessel with the mass and the precise point at which the vessel penetrates the mass. Finally, as concerned coronary artery visualization, this was a crucial preoperative aspect. On the basis of CT examination, which excluded suspected coronary artery disease, major thoracic surgery could be planned and performed without any invasive procedure. REFERENCES 1. Rosado-de-Christenson ML, Galobardes J, Moran CA. Thymoma: radiologic-pathologic correlation. Radiographics. 1992;12: 151–168. 2. Maher MM, Shepard JA. Imaging of thymoma. Semin Thorac Cardiovasc Surg. 2005;17:12–19. 3. Do YS, Im J-G, Lee BH, et al. CT findings in malignant tumors in thymic epithelium. J Comput Assist Tomogr. 1995;19: 192–197. 4. Andreini D, Pontone G, Ballerini G, et al. Feasibility and diagnostic accuracy of 16-slice multidetector computed tomography coronary angiography in 500 consecutive patients: critical role of heart rate. Int J Cardiovasc Imaging. 2007;23: 789–801. 5. Pontone G, Andreini D, Ballerini G, et al. Diagnostic work-up of unselected patients with suspected coronary artery disease: complementary role of multidetector computed tomography, symptoms and electrocardiogram stress test. Coronary Artery Dis. 2007;18:265–274. 6. Andreini D, Pontone G, Pepi M, et al. Diagnostic accuracy of multidetector computed tomography coronary angiography in patients with dilated cardiomyopathy. J Am Coll Cardiol. 2007;49:2044–2050.
33
