Thymoma: a clinicopathologic study based on the new World Health Organization classification.
OBJECTIVE
This study explored the relationship between the histologic subtype of thymoma according to the new World Health Organization histologic classification and the clinical findings, as well as the prognostic significance of the classification.


METHODS
A total of 130 patients with thymoma, who underwent resection at the National Cancer Center Hospital, Tokyo, from 1962 to 2000, were studied retrospectively. The histologic subtype of thymoma was determined according to the new World Health Organization histologic classification. The stage was also determined according to a modified Masaoka's classification as stage I, II, III, IVa, or IVb. To determine the factors that may affect the prognosis of thymoma, a multivariate analysis with Cox's proportional hazards regression model was performed.


RESULTS
The distribution of histologic subtype was type A (n = 18), type AB (n = 56), type B1 (n = 15), type B2 (n = 29), and type B3 (n = 12). A close correlation was seen between the histologic subtype and stage (P =.000). The overall survivals at 5 and 10 years were 92% and 91%, respectively. The 5- and 10-year survivals according to stage were 100% and 100% (stage I, n = 40; stage II, n = 54), 81% and 76% (stage III, n = 25), and 47% and 47% (stage IV, n = 11), respectively. The difference in survival between stage III and stage IV was significant (P =.000). Patients with type A or AB thymoma demonstrated a 100% survival at both 5 and 10 years. Recurrences were seen in 12 patients with complete resection. According to a multivariate analysis, tumor size (P =.001), completeness of resection (P =.002), histologic subtype (P =.011), and stage (P =.00) were significant prognostic factors.


CONCLUSIONS
The World Health Organization histologic classification significantly correlated with the clinical stage. Tumor size, completeness of resection, histologic subtype, and stage predicted the prognosis of thymoma.
Nakagawa
Kazuo
K
Divisions of Thoracic Surgery, National Cancer Center Hospital and Research Institute, Tokyo, Japan.
Asamura
Hisao
H
Matsuno
Yoshihiro
Y
Suzuki
Kenji
K
Kondo
Haruhiko
H
Maeshima
Arafumi
A
Miyaoka
Etsuo
E
Tsuchiya
Ryosuke
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D015996:Survival Rate; D013945:Thymoma / Q000145:classification* / Q000401:mortality / Q000473:pathology*; D013953:Thymus Neoplasms / Q000145:classification* / Q000401:mortality / Q000473:pathology*; D014944:World Health Organization