Evolution to malignancy in a recurrent meningioma: morphological and cytogenetic findings.

The original tumor and 4 relapses of a recurrent meningioma were studied. We analyzed and compared these recurrences by histopathology, PCNA labelling index (PCNA-LI), nuclear count, and cytogenetical findings. The most important changes in the evolution to aggressivity were: recurrences at progressively shorter intervals, increases in the PCNA-LI, and micronecrosis; histological changes such as sheeting and increase of the extracellular matrix and a gradual transformation to a clonally complex karyotype.