Abstract

We report 4 cases of malignant thymoma which were composed of 2 cases of invasive thymoma and 2 cases of thymic carcinoma. The cytologic findings of invasive thymoma were similar to those of benign thymoma. The distinctive cytologic features of thymic carcinoma were necrotic background, irregular clusters and individually scattered arrangement of anaplastic epithelial cells, and some scattered mature small lymphocytes. These findings may be found in the Hodgkin'slymphoma, seminoma, and metastatic squamous cell carcinoma, undifferentiated carcinoma, and large cell carcinoma of the. lung. But, the feature of irregular clustering of anaplastic epithelial cell having scanty cytoplasm was different from Hodgkin'slymphoma and seminoma. Clinical and radiologic findings as well as cytologic finding were helpful in differential diagnosis of thymic carcinoma from metastatic carcinoma.

• Keywords: Malignant thymoma;Invasive thymoma;Thymic carcinoma;Aspiration cytology