Chest
Volume 127, Issue 3, March 2005, Pages 755-761
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Clinical Investigations: Tumors
Prognostic and Clinical Relevance of the World Health Organization Schema for the Classification of Thymic Epithelial Tumors: A Clinicopathologic Study of 108 Patients and Literature Review

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Study objectives

Controversy has ensued about the prognostic relevance of the new World Health Organization (WHO) schema for the classification of thymoma. In this study, we present the clinical and histologic features of 108 thymomas and evaluate the usefulness of this histologic schema in view of the prognosis

Design

Retrospective, clinicopathologic analysis of our experience and a review of recent literature

Setting

Department of Thoracic and Cardiovascular Surgery of a university hospital

Methods

A series of 108 thymomas were reviewed and classified by the new WHO schema. The clinical characteristics and the survival outcome were investigated in reference to the WHO subtypes. The Cox proportional hazards model was applied to determine the factors affecting the tumor-related survival. Recent literature on the prognostic relevance of the WHO schema was reviewed

Results

There were 7 type A tumors, 25 type AB tumors, 12 type B1 tumors, 32 type B2 tumors, 20 type B3 tumors, and 12 type C tumors. The histologic subtype closely correlated with the Masaoka stage (p = 0.00). The tumor-related survivals at 5 years and 10 years were 88.0% and 77.9%, respectively. Stage III and IV tumors had a significantly worse prognosis than stage I or II tumors (p < 0.05). Type B3 tumors had an intermediate prognostic ranking in comparison with the carcinomas and with the other groups. On multivariate analysis, the WHO subtype (A-B2 vs B3 vs C) could predict the tumor-related survival, but the Masaoka stage was the most important prognostic factor affecting the postoperative survival (p = 0.026)

Conclusion

The Masaoka stage is the most important determinant of survival in surgically resected cases of thymoma. To clarify the prognostic relevance and clinical usefulness of the WHO schema, consistent parameters reflecting the surgical outcome and development of the diagnostic tools that could improve the interobserver agreement within type B are needed

Section snippets

Patients and Surgical Strategy

One hundred twenty-six consecutive patients with thymoma were treated at our institute during the period from January 1992 to June 2002. Eighteen patients were excluded from the study: 6 patients who were initially treated elsewhere, 4 patients who received preoperative chemotherapy or radiotherapy, 7 patients in whom open biopsy alone was performed, and 1 patient who died of sepsis after operation. Therefore, a total of 108 cases of thymoma were considered for review.

Our goals in the surgical

Clinical Features

There were 63 male patients (58.3%) and 45 female patients (41.7%), with a mean age of 46.5 ± 13.8 years (± SD) [range, 20 to 83 years]. Fifty-one patients (47.2%) were in stage I, 35 patients (32.4%) were in stage II, 13 patients (12.0%) were in stage III, and 9 patients (8.3%) were in stage IV. MG was associated in 44 patients (40.7%). The treatment profiles of these 108 patients are summarized in Table 1. Our strategies in the adjuvant therapy were as follows: no adjuvant therapy in stage I

Discussion

In this study, the histologic subtype based on the WHO classification could be determined in all the 108 patients. Among the histologic subtypes, the most frequent histologic subtype was type B2 (29.6%), followed by type AB (23.1%). In our series, type A was more unusual (seven cases, 6.5%) than those in the other studies,12, 14, 16, 17 which reported the proportion of type A to be 13.8 to 22.0%. Although a larger proportion of the type A thymoma in other studies might result from a failure to

Conclusion

In the present study, the Masaoka stage is the most important determinant of survival in the thymoma patients. A prognostic value of the WHO histologic classification was noted when the schema was simplified and to bring the entity into three subgroups (A-B2/B3/C). To clarify the prognostic relevance and clinical usefulness of the WHO schema, certain prerequisites or consensus are necessary in the future studies.

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