THERE HAS BEEN continuing debate on the subject of malignant meningiom
as, but few studies of large series have been reported. We present our
experiences with 25 atypical and malignant meningiomas operated on at
Henry Ford Hospital between 1976 and 1990. A total of 319 primary int
racranial meningiomas were operated on during this period; of these, 2
94 (92%) were benign, 20 (6.26%) atypical, and 5 (1.7%) malignant. We
used a modified histological grading system, based primarily on World
Health Organization criteria of malignancy (hypercellularity, loss of
architecture, nuclear pleomorphism, mitotic index, tumor necrosis, and
brain invasion), to define atypical and malignant meningiomas. Each o
f these criteria was given a score from 0 to 3, and then partial score
s were added to obtain cumulative scores. These total scores were then
used to determine what is benign, atypical, and malignant. The peak i
ncidence of atypical and malignant meningiomas was in the seventh and
sixth decades, respectively. The predominance of female patients with
benign meningiomas was not observed in the nonbenign group. The male:f
emale ratio for atypical and malignant meningiomas was 1:0.9 versus 1:
2.3 for benign meningiomas (P = 0.024). The most common presenting sym
ptom and physical sign in our patients was paresis. In reviewing their
radiographic features, all patients showed moderate or marked edema o
n computed tomography. Calcification was exhibited by one patient only
and ''mushrooming'' was seen in three cases. Of the 25 patients, 11 (
44%) died during follow-up: 2 in the perioperative period, 8 within th
e first 5 years, and 1 died 11 years after the diagnosis. There were r
ecurrences in 14 cases (51.85%), 10 (71.42%) of which had undergone gr
oss total resection. Tumor recurrence was accompanied by dedifferentia
tion from a more benign histological finding in five cases (1.63% of t
he total number of meningiomas). The 5-, 10-, and 15-year recurrence r
ates each were 50% for atypical meningiomas and 33%, 66%, and 100% for
malignant meningiomas. These recurrence rates far exceeded those for
benign meningiomas, which were 2% each (P = 0.0001). Radiation therapy
did not prevent or delay the recurrence of tumors. However, because t
here were a small number of patients receiving radiation therapy in ou
r series, we cannot conclude that radiation therapy has no role in the
postoperative management of meningiomas.