Suster and Moran correlate thymic epithelial neoplasms with morphologic and functional features of the thymus. Our present understanding of the thymus is incomplete. 19 Suster and Moran advocate a category of moderately differentiated thymic epithelial neoplasm, or atypical thymoma. This group would include the predominantly epithelial thymomas of the traditional classification, which, according to many studies, are more likely to recur than other types of thymoma. The poorly differentiated thymic tumors are the carcinomas, which are more likely to metastasize.
Thymic neoplasms are unique.
The effort to correlate thymoma histopathology with thymus histology has a long history. Many of the concepts on which the classification was based were subsequently shown to be erroneous, and the classification was never widely accepted. In my opinion, the cortical-medullary classification of thymomas is inaccurate and confusing, and should be abandoned. Rather than simplifying the pathology of thymic neoplasms, the Suster and Moran proposal introduces further complicating concepts. The traditional classification based on invasiveness, number of lymphocytes, and epithelial cell architecture is descriptive but straightforward.