Classification

Based on the tumor location, degree of tumor spread, tumor characteristics, and anatomical characteristics of the thoracic vertebrae, we propose the classification of thoracic dumbbell tumors. We divided the thoracic vertebrae into three areas (A, B, C) in the horizontal position: area A was medial to the midline in the intervertebral foramen, area B was the area between the midline in the intervertebral foramen, and the vertical line through the costo-transverse joint lateral margin, and area C was lateral to the vertical line through the costo-transverse joint lateral margin. According to these areas, we formulated three types of dumbbell tumors: type I, the largest transverse sections of the tumor were located in area A (Fig. 1A) or both areas A and B (Fig. 1B); type II, the largest transverse sections of the tumor were located in area B (Fig. 2A) or both areas B and C (Fig. 2B); and type III, the largest transverse sections of the tumor were located in areas A, B, and C. In addition, depending on whether the dura was slit to access the intradural component, it was classified into two subtypes: type IIIA (Fig. 3A), in which the intradural dura was removed, and type III B (Fig. 3B), in which there was no need to open the dura.

For type I tumors, the largest transverse sections are located in area A or A and B. A The tumor was located in area A. B The tumor was located in areas A and B

For type II tumors, the largest transverse sections are located in area B or areas B and C. A The tumor was located in area B. B, The tumor was located in areas B and C

For type III tumors, the largest transverse sections are located in areas A, B, and C. A The tumor was intradurally located in the dura and extended to areas B and C. B The tumor was not intradurally located in the dura nor extended to areas B and C