Thymoma: A pathological study of 50 cases

BACKGROUND: A combination of epithelial cells and lymphocytes results in a varied histomorphology of thymomas and consequent varied classification systems.
AIM: To correlate the Marino and Muller-Hermelink (MMH) classification with the invasive behaviour of thymomas.
SETTING AND DESIGN: Retrospective analysis.
MATERIALS AND METHOD: Thymomas encountered in the past 21 years were re-classified with the MMH classification and correlated with Masaoka's staging and clinical presentation.
RESULTS: The thymomas formed 91% of the primary thymic epithelial tumours. Predominantly cortical thymomas (n=21) and cortical thymomas (n=22) were the common subtypes and 60% and 77% of these, respectively, were in stages II or III. Cystic change, necrosis or haemorrhage played no role in predicting invasive behaviour. Cortical epithelium correlated well with the presence of para-thymic syndromes, especially myasthenia gravis.
CONCLUSION: MMH classification is easy to apply. Cortical thymomas in stage I should be followed up for possible recurrence.