Thymoma--the usefulness of some prognostic factors for diagnosis and surgical treatment

The aim of the study was to identify prognostic factors which could help evaluate both the treatment offered to patients with thymoma and late results.

Forty patients were treated for mediastinal thymoma. The patients were staged clinico-pathologically (according to Masaoka) on the basis of the retrospective analysis of their operation protocols as follows: seven (17.5%)-stage I, 19 (22. 5%)-stage II, 17 (42.5%)-stage III, seven (17.5%)-stage IV. Analysis of DNA contents in cell nuclei of 23 thymomas was performed by the flow cytofluorometric method.

From the whole group of patients, 65% survived for 5 years, 55% survived for 10 years and 43% survived for 15 years. We noted significant differences in survival time between stage I and stage IV (P<0.0012); stage II and stage IV (P<0.0006), as well as between stage III and stage IV (P<0. 005). Significantly worse prognosis was observed in the case of cortical thymomas as compared with medullary or mixed types (P<0. 0001 P<0.002). Analysis of DNA content showed signficantly higher probability of survival for the patients who had DI=1.0 (diploid), as compared with DNA >1.0 (aneuploid) (P<0.006). Of the 11 patients with diploid tumours, 91% survived for 5 years, but of the 12 aneuploid, only 23% survived.

The most important positive prognostic factors influencing survival rate in patients with thymoma are: lower stage, medullary type (according to Muller-Hermelink classification), possibility of performing complete resection, diploidal nature of the tumour. Multivariate analysis of survival revealed clinico-pathological stage (according to Masaoka) and histological type (according to Salyer) as significantly independent prognostic factors.