Abstract
The recurrence of meningiomas in 89 cases which were operated on and followed up are discussed in this paper. The recurrence rate of meningiomas was 22% in all cases, 13% in cases of complete removal (Simpson's grades I & II) and 55% in cases of incomplete removal (Simpson's grades III, IV & V). The most probable cause affecting the recurrence was the operative method in which the tumors were completely or incompletely removed.
The recurrence rate of meningiomas in each histological subtypes after complete removal was as follows: 33% in fibroblastic, 13% in meningotheliomatous, and none in angioblastic and atypical types. When they were diagnosed at the first operation, there were no significant differences in the histological subtypes among the recurrent and non-recurrent meningiomas, and those which became malignant after repeated operation.
While most recurrent meningiomas did not change their basic morphological types, 25% in the recurrent tumors, or 5.6% in the total series, showed malignant transformation. The averag. interval of time between the first and the second operation was 31 months, and the intervals became shorter with consecutive operations. The intervals between the first and the second operations of tumors with no malignancy ranged from 5 to 13 years.
Histological features in malignant transformation of tumors were: 1) the lack of normal arrangements of tumor cell, 2) increased mitotic rate, 3) focal necrosis, and 4) cortical and bone invasion.
One case was initially diagnosed as fibroblastic meningioma but finally as sarcoma.
