Proposal for a new mediastinal compartment classification of transverse plane images according to the Japanese Association for Research on the Thymus (JART) General Rules for the Study of Mediastinal Tumors

Abstract

There is no existing worldwide published method for mediastinum compartment classification based on transverse section images for the differential diagnosis of mediastinal tumors. Herein, we describe a new method for anatomic mediastinal compartment classification using transverse section computed tomography (CT) images and the use of this method to classify mediastinal lesions, and thus evaluate whether the method is sufficiently user-friendly and useful. In a publication of the Japanese Association for Research on the Thymus (JART), we proposed the following four mediastinal compartments based on transverse CT images: superior portion of mediastinum, anterior mediastinum (prevascular zone), middle mediastinum (peri-tracheoesophageal zone), and posterior mediastinum (paravertebral zone). In the present study, we retrospectively analyzed 445 pathologically proven mediastinal mass lesions, and categorized them into the proposed four compartments by consensus reading. Mass lesions were classified into compartments based on the location of the lesion centroid, and each lesion was satisfactorily categorized into a compartment. Almost all thymic epithelial tumors (99%, 244/246), all 24 thymic malignant lymphomas and a majority of germ cell neoplasms (93%, 54/58) were classified as being in the anterior mediastinum compartment. The majority of intrathoracic goiters (82%, 14/17) were categorized as being in the superior portion of the mediastinum compartment. Approximately two-thirds of mass lesions in the middle mediastinum were cysts, including foregut and pericardial cysts. Approximately 80% of 37 mass lesions in the posterior mediastinum were neurogenic tumors. Correspondingly, 29 of the 49 neurogenic tumors (60%) were categorized as being in the posterior mediastinum, while 10 (20%) were in the superior portion of the mediastinum, 4 (8%) in the anterior mediastinum, and 6 (12%) in the middle mediastinum. Our findings showed that the newly proposed mediastinal compartment classification using transverse images appears to be user-friendly enough for practical clinical application and may be helpful in differential diagnoses.

Figure 1

Schematic diagram represents the new proposal for mediastinal compartment classification according to the General Rules for Study of Mediastinal Tumors of the Japan Association for Research on the Thymus (JART). (A) Thoracic inlet, (B) upper rim of clavicle, (C) sterno-clavicular joint, (D) left brachiocephalic vein across TML, (E) aortic arch, (F) tracheal carina, (G) right main pulmonary artery, (H) pulmonary trunk, (I) left atrium, (J) tricuspid valve. Abbreviations: CL, clavicle; Tr, trachea; SCA, subclavian artery; SCV, subclavian vein; 1R, first rib; 2R, second rib; Ster, sternum; E, esophagus; RBCV, right brachicephalic vein; RBCA, right brachiocephalic artery; LBCV, left brachicephalic vein; LCCA, left common carotid artery; LSCA, left subclavian artery; SVC, superior vena cava; AA, aortic arch; AsA, ascending aorta; LPA, left pulmonary artery; ITV, internal thoracic vessels; Br, bronchus; LSPV, left superior pulmonary vein; RSPV, right superior pulmonary vein; PA, pulmonary artery; RA, right atrium; RIPV, right inferior pulmonary vein; LIPV, left inferior pulmonary vein; LA, left atrium; TML, tracheal mid-line; M-PBL, middle-posterior boundary line (see Materials and methods).

Figure 1

Schematic diagram represents the new proposal for mediastinal compartment classification according to the General Rules for Study of Mediastinal Tumors of the Japan Association for Research on the Thymus (JART). (A) Thoracic inlet, (B) upper rim of clavicle, (C) sterno-clavicular joint, (D) left brachiocephalic vein across TML, (E) aortic arch, (F) tracheal carina, (G) right main pulmonary artery, (H) pulmonary trunk, (I) left atrium, (J) tricuspid valve. Abbreviations: CL, clavicle; Tr, trachea; SCA, subclavian artery; SCV, subclavian vein; 1R, first rib; 2R, second rib; Ster, sternum; E, esophagus; RBCV, right brachicephalic vein; RBCA, right brachiocephalic artery; LBCV, left brachicephalic vein; LCCA, left common carotid artery; LSCA, left subclavian artery; SVC, superior vena cava; AA, aortic arch; AsA, ascending aorta; LPA, left pulmonary artery; ITV, internal thoracic vessels; Br, bronchus; LSPV, left superior pulmonary vein; RSPV, right superior pulmonary vein; PA, pulmonary artery; RA, right atrium; RIPV, right inferior pulmonary vein; LIPV, left inferior pulmonary vein; LA, left atrium; TML, tracheal mid-line; M-PBL, middle-posterior boundary line (see Materials and methods).

Figure 2

Contrast-enhanced CT images represent new proposal of mediastinal compartment classification according to the General Rules for Study of Mediastinal Tumors of the JART. (A) Thoracic inlet, (B) upper rim of clavicle, (C) sterno-clavicular joint, (D) left brachiocephalic vein across TML, (E) aortic arch, (F) tracheal carina, (G) right main pulmonary artery, (H) pulmonary trunk, (I) left atrium, (J) tricuspid valve, (K) hepatic dome of diaphragm, (L) middle of 12th thoracic vertebral body. Abbreviations: TML, tracheal mid-line; M-PBL, middle-posterior boundaryline (see Materials and methods).

Figure 2

Contrast-enhanced CT images represent new proposal of mediastinal compartment classification according to the General Rules for Study of Mediastinal Tumors of the JART. (A) Thoracic inlet, (B) upper rim of clavicle, (C) sterno-clavicular joint, (D) left brachiocephalic vein across TML, (E) aortic arch, (F) tracheal carina, (G) right main pulmonary artery, (H) pulmonary trunk, (I) left atrium, (J) tricuspid valve, (K) hepatic dome of diaphragm, (L) middle of 12th thoracic vertebral body. Abbreviations: TML, tracheal mid-line; M-PBL, middle-posterior boundaryline (see Materials and methods).