Rationale and Objectives
Both preoperative computed tomography (CT) staging and postoperative surgical Masaoka clinical staging are of great clinical importance for diagnosing thymomas. Our study aimed to investigate the relationships between these two staging systems.
Materials and Methods
This was a retrospective review of 129 patients who had undergone thymoma surgery. Helical CT and 16-slice CT were performed preoperatively. Surgical findings were evaluated according to the Masaoka clinical staging system.
Results
A significant association was shown between Masaoka clinical staging and CT staging, especially of features including tumor size ( P = .004), tumor shape ( P < .001), tumor density ( P < .001), capsule completeness ( P < .001), and involvement of surrounding tissues ( P < .001). Based on the CT findings, there were 35.09% of Masaoka stage I patients who had a tumor size <5 cm as compared to 14.81% of stage IV patients. Only 8.77% of Masaoka stage I patients had a tumor size ≥10 cm as compared to 40.74% of stage IV patients. In stages III and IV, most tumors were irregularly shaped with an uneven density and incomplete capsule. Invasive tumors were more frequently found in stages III (81.48%) and IV (88.89%) than in stages I (0%) and II (38.89%). The incidence of myasthenia gravis was comparable in different stages. Consistency between CT and Masaoka clinical stages was higher in stage I (37.98%) than other stages (approximately 10%).
Conclusion
This study documented a close relationship between preoperative CT thymoma staging and postoperative Masaoka clinical staging. Thus, preoperative CT findings can be beneficial for determining the proper management and prognosis of thymoma patients.
Thymomas are tumors of epithelial cell origin arising from the thymus gland. Although thymomas are rare, occurring in only about 0.15 per 100,000 population , they account for 15% to 21.7% of tumors in the mediastinum and 47% of tumors in the anterior mediastinum . Clinical presentation of thymomas may vary considerably, but they are usually accompanied by either an immune or nonimmune mediated paraneoplastic syndrome, of which myasthenia gravis (MG) is the most common presentation .
The clinical stage of thymoma is analyzed based on the Masaoka staging system and is usually determined according to surgical findings . The histologic classification system, which was introduced by the World Health Organization (WHO) in 1999 and updated in 2004 , is based on the pathological findings after collecting the specimen by either biopsy or during surgery. These two systems are applied at the postoperative stage and are considered independent prognostic indicators . However, there is no unequivocal correlation between WHO classification and Masaoka stages . The preoperative distinction of thymoma is also of great clinical importance; it is critical for the determination of a proper therapeutic regimen, which will necessarily vary for different stages of thymomas . Regarding the role of radiographic imaging modalities in thymoma assessment, a recent study showed that computed tomography (CT) was currently the first choice for characterizing mediastinal masses in terms of anatomic features and invasiveness of surrounding structures at the preoperative staging of thymoma . The standard way to assess patient responses to therapy is tumor measurement by CT according to the Response Evaluation Criteria in Solid Tumors guidelines . CT is helpful in differentiating invasive from noninvasive thymoma; the presence of lobulated or irregular contours, areas of low attenuation, and multifocal calcifications is suggestive of invasive thymoma . The primary tumor CT imaging features can differentiate between stage I/II and stage III/IV disease, helping to identify patients more likely to benefit from neoadjuvant therapy . However, correlation between CT scan results and the WHO classification system remains controversial . Studies on the correlation between preoperative CT findings and Masaoka clinical stage of thymomas are limited .
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Materials and methods
Participants and CT Scanning
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Features Analyzed by CT
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Table 1
Characteristics and Clinical Features of 129 Patients
Variable n = 129 Characteristics Age (y) 47.98 ± 12.54 Gender (male) 64 (49.61%) Symptoms Chest tightness and chest pain 46 (35.66%) Cough 24 (18.60%) Fever 4 (3.10%) Edema 4 (3.10%) CT features Tumor size (cm) <5 33 (25.58%) 5–10 70 (54.26%) ≥10 26 (20.16%) Irregular shape 85 (65.89%) Uneven density 70 (54.26%) Calcification 27 (20.93%) Necrotic or cystic components 32 (24.81%) Incomplete capsule 63 (48.84%) Involvement of surrounding tissues 53 (41.09%) Lymph node enlargement 31 (24.03%) CT stage I 55 (42.64%) II 31 (24.03%) III 25 (19.38%) IV 18 (13.95%) Clinical status Myasthenia gravis 42 (32.56%) Resectable tumor 118 (91.47%) Masaoka clinical stage I 57 (44.19%) II 18 (13.95%) III 27 (20.93%) IV 27 (20.93%)
CT, computed tomography.
Data were expressed as mean ± SD for age; data were represented as counts (percentages) for categorical variables.
Table 2
The Association between CT Features and Masaoka Clinical Stage
CT Features Masaoka Clinical Stage P Value I II III IV Tumor size (cm) .004 ∗ <5 20 (35.09%) 5 (27.78%) 4 (14.81%) 4 (14.81%) 5–10 32 (56.14%) 12 (66.67%) 14 (51.85%) 12 (44.44%) ≥10 5 (8.77%) 1 (5.56%) 9 (33.33%) 11 (40.74%) Shape <.001 ∗ Oval 37 (64.91%) 6 (33.33%) 1 (3.7%) 0 (0%) Irregular 20 (35.09%) 12 (66.67%) 26 (96.3%) 27 (100%) Density <.001 ∗ Even 37 (64.91%) 8 (44.44%) 8 (29.63%) 6 (22.22%) Uneven 20 (35.09%) 10 (55.56%) 19 (70.37%) 21 (77.78%) Capsule <.001 ∗ Complete 56 (98.25%) 5 (27.78%) 5 (18.52%) 0 (0%) Incomplete 1 (1.75%) 13 (72.22%) 22 (81.48%) 27 (100%) Involvement of surrounding tissues <.001 ∗ Yes 0 (0%) 7 (38.89%) 22 (81.48%) 24 (88.89%) No 57 (100%) 11 (61.11%) 5 (18.52%) 3 (11.11%) Lymph node enlargement .272 Yes 47 (82.46%) 14 (77.78%) 20 (74.07%) 17 (62.96%) No 10 (17.54%) 4 (22.22%) 7 (25.93%) 10 (37.04%)
CT, computed tomography.
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Table 3
The Association between Masaoka Clinical Stage and Myasthenia Gravis
Myasthenia Gravis Masaoka Clinical Stage P Value I II III IV No 39 (30.23%) 11 (8.53%) 15 (11.63%) 22 (17.05%) .211 Yes 18 (13.95%) 7 (5.43%) 12 (9.3%) 5 (3.88%)
Data were expressed as counts (percentages). The association was conducted by a chi-square test.
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CT Tumor Staging
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Masaoka Staging of Surgical Findings
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Statistical Analysis
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Results
Patient Demographic and Clinical Data
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Distribution of CT Features among Clinical Stages
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Consistency between CT Stage and Clinical Stage
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Table 4
Consistency between CT Stage and Masaoka Clinical Stage
CT Stage Masaoka Clinical Stage I II III IV I 49 (37.98%) 3 (2.33%) 3 (2.33%) 0 (0%) II 8 (6.20%) 13 (10.08%) 7 (5.43%) 3 (2.33%) III 0 (0%) 1 (0.78%) 13 (10.08%) 11 (8.53%) IV 0 (0%) 1 (0.78%) 4 (3.10%) 13 (10.08%)
CT, computed tomography.
Weighted kappa coefficient = 0.819.
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Discussion
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Limitations
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Conclusion
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