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Type A and AB thymomas: histological features associated with increased stage
Anna C Green1, Alexander Marx, Philipp Ströbel
1Department of Histopathology, Royal Brompton and Harefield Hospitals NHS Foundation Trust, London, UK.
Histopathology
|November 11, 2014
Summary
This study found that while most thymomas (type A and AB) are benign, some rare cases exhibit aggressive behavior. Necrosis presence may predict more advanced thymoma disease.
Area of Science:
- Oncology
- Pathology
Background:
- The World Health Organization (WHO) classification designates thymoma types A and AB as benign.
- Emerging evidence suggests rare instances of aggressive behavior in these thymoma subtypes.
Purpose of the Study:
- To determine the frequency of atypical features in thymoma types A and AB.
- To investigate the association between atypia and advanced thymoma disease stages.
Main Methods:
- Retrospective review of 121 thymomas (68 type A, 53 type AB).
- Assessment for atypical features: nuclear pleomorphism, mitotic activity, and necrosis.
- Logistic regression analysis to correlate features with Masaoka-Koga stage; follow-up data reviewed.
Main Results:
- Necrosis was significantly associated with increased Masaoka-Koga stage in both univariate and multivariate analyses.
- Nuclear pleomorphism and increased mitotic activity did not correlate with advanced disease stages.
- 72 stage I, 42 stage II, 5 stage III, and 2 stage IV thymomas were identified.
Conclusions:
- Atypical variants of type A and AB thymoma can exhibit more aggressive behavior.
- Necrosis is a potential predictor of aggressive behavior in thymomas.
- Re-evaluation of the WHO classification regarding the behavior of thymoma types A and AB may be warranted.
