Infantile hemangioendothelioma of the thymus with massive pleural effusionand Kasabach-Merritt syndrome: Histopathological, flow cytometrical analysis of the tumor

Infantile hemangioendothelioma of the thymus is a rare disease. We describe a patient who developed a large anterior mediastinal mass, severe thrombot ytopenia and massive pleural effusion at 1 month of age. Glucocorticosteroi d and irradiation therapy had no effect on either the tumor size or clinica l symptoms and the tumor was resected subtotally. Three months after the su btotal resection, the remaining tumor had almost disappeared and the sympto ms had resolved. The patient has now been well far 1 year after surgery wit hout evidence of recurrence. The tumor tissue was characterized by prominen t vascular endothelial proliferation intermixed with a normal thymic struct ure, producing a picture consistent with that of an infantile hemangioendot helioma in the thymus. Immunohistochemically, the tumor cells showed positi ve staining for vimentin, factor Vm and CD34. The DNA stemline and prolifer ative activity were examined by how cytometry, which revealed a diploid ste mline with a low growth fraction. DNA content and cell cycle analyses of th e tumor tissue may be useful for predicting the biological behavior of the tumor.