A Retrospective Study of 25 Cases of Thymic Epithelial Tumors Treated in Tsuchiura Kyodo General Hospital / 日本農村医学会雑誌

ABSTRACT

Thymic epithelial tumors are treated with reference to the Masaoka staging system. In 1999, the World Health Organization published a histologic classification of thymomas. The WHO classification was revised in 2004. There is a general consensus that it is as important a prognostic factor in primary thymoma and thymic carcinoma patients as the Masaoka staging system. In the present study, a total of 25 cases of thymic epithelial tumors (21 thymoma cases and 4 thymic carcinoma cases) treated from 1991 through 2005 in our hospital were reclassified based on the new WHO classification. The thymoma cases consisted of four at Masaoka's stage I, 11 cases at stage II and six cases at stage III, whereas according to the WHO classification they were categorized into seven B1 type tumors, eight B2 type, four B3 type and two unclassifiable cases. Of the four thymic carcinoma cases, one belonged under Masaoka's stage II, another under stage III and two under stage IV. One thymic carcinoma case resulted in death. There were no fatalities from thymomas. Most of the thymomas at Masaoka's stage III came under WHO type B2 and B3, showing a high incidence of local infiltration. Since either the WHO classification or the Masaoka staging system is an important factor for determining the course of treatment, we concluded that both should be utilized clinically.