Table 1 Suster and Moran classification of thymic epithelial neoplasms.

Tumour type	Grading	Histological criteria
Thymoma	Well differentiated	Preservation of organotypical features of thymic differentiation; no cytological evidence of atypia
Atypical thymoma	Moderately differentiated	Partial preservation of organotypical features of differentiation; mild to moderate cytological atypia
Thymic carcinoma	Poorly differentiated	Loss of organotypical features of differentiation; presence of overt cytological evidence of malignancy

Reprinted with permission from Suster and Moran.¹⁷