Prognostic importance of histomorphologic subclassification for epithelial thymic tumors.

BACKGROUND

The prognostic importance of various clinical variables (age, sex, association with myasthenia gravis), staging according to Masaoka, histologic type according to the Marino/Kirchner/Müller-Hermelink (MKM-H) classification, and residual tumor category (R category) was evaluated in a retrospective analysis.

METHODS

Eighty-two patients with epithelial thymic tumors (ETTs) treated in the period 1969-1993 were evaluated, and archived specimens were histologically reclassified according to the classification of MKM-H.

RESULTS

Age, sex, and association with myasthenia gravis were of no prognostic importance. The R category is of significant prognostic importance, with 5- and 10-year survival rates of 93.6% and 87.3%, respectively, for R0 resections compared with 0% at 5 years for R1 and R2 resections (p < 0.001). Staging (Masaoka) proved to be a prognostic factor (5-/10-year survival: stage I, 100%/90.9%; II, 95%/88.2%; III, 55.9%/46.6%; and IV, 10.8%/ 10.8%; p < 0.001). Histologic typing according to MKM-H is also of significant prognostic importance (5/10 year survival: thymomas: medullary, 100%/100%; mixed, 100%/100%, predominantly cortical, 68.6%/68.6%; cortical, 65.8%/65.8%; thymic carcinomas: well-differentiated type, 62.3%/44.5%; thymic carcinomas other than well-differentiated type, 33.6%/26.9%; p < 0.001). Multivariate analysis demonstrated that staging (p < 0.001), R category (p < 0.026), and MKM-H classification (p < 0.028) have an independent impact on survival.

CONCLUSIONS

Staging (Masaoka), R category, and histologic classification (MKM-H) are important independent prognostic factors for patients with epithelial thymic tumors. Complete (R0) surgical resections should be the ultimate goal in the clinical management of patients with epithelial thymic tumors.