Adjacent astrocytoma and ependymoma: dependent mixed neoplasia or unusual collision tumors?

Concurrent neoplastic transformation of different cellular elements resulting in an intraventricular and intraparenchymal tumor is described. An infiltrating astrocytoma of the left frontal lobe had been partially removed from a 43-yr-old woman. Four months later she died, and the autopsy revealed a recurrent astrocytoma and a closely apposed large intraventricular ependymoma. Both light microscopy and ultrastructural findings established the different nature of the two tumors. Theoretically they could represent collision or composite tumors. Another possibility would be that a relatively longstanding ependymoma induced the astrocytic neoplasm. The clinical history and the sequential morphological analysis, i.e., biopsy and autopsy sampling suggest that the ependymoma developed due to the inductive influence of the astrocytic growth.