Table 1. The World Health Organization histopathological classification of thymic epithelial tumours
TypePathological featuresInvasiveness %10-yr disease-free survival %
ASpindle or polygonal cell lacking atypia10–40100
Resembles medullary thymoma with paucity of immature thymocytes
ABMixed pattern of type A (lymphocyte-poor) and type B (lymphocyte-rich) thymoma30–40100
Immature and mature lymphocytes
B1Thymoma resembling the cortical thymus45–50
B2Subtypes B1, B2 and B3 differentiated by an increasing epithelial/lymphocyte ratio and the emergence of atypia65–7085
B3Mature lymphocytes85–9035
Thymic carcinomaEpithelial cell atypia90–9515
Absence of immature lymphocytes
Frequent expression of CD5/KIT
  • Adapted from [3].