Population-based analysis of sporadic and type 2 neurofibromatosis-associated meningiomas and schwannomas

Objective: To estimate the incidence of meningiomatosis and schwannomatosis , and their familial occurrences and relation to type 2 neurofibromatosis ( NF2) in a well-defined population. Methods: Patients with histologically ve rified intracranial, spinal, or peripheral schwannomas or meningiomas, who were residents of the Helsinki University Hospital catchment area (populati on, 1,713,000) from January 1, 1985, to December 31, 1995, were included in the study. The Population Register Center was used to identify relatives o f all the patients, and their data were linked further to the Finnish Cance r Registry to find NF2-related tumors. Detailed pedigrees were constructed for the patients with NF2, schwannomatosis, meningiomatosis, patients with relatives with histologically verified schwannomas or meningiomas, and pati ents younger than 25 years of age at the time of diagnosis. Results: Approx imately 3% (12 of 455) of the schwannoma patients had multiple schwannomas in association with NF2, and 2% (11 of 455) had schwannomatosis without NF2 . Two of the patients with schwannomatosis (2 of 11) had familial schwannom atosis. Approximately 1% (7 of 823) of the patients with meningioma had mul tiple meningiomas in association with NF2, and 4% (29 of 823) had meningiom atosis without NF2. No families with meningiomatosis were found among the 8 23 patients with meningioma studied. The birth occurrence of NF2 was 1 in 8 7,410. Conclusions: The current diagnostic criteria of type 2 neurofibromat osis (NF2) seem valid because NF2 patients were differentiated rather easil y from patients with sporadic schwannomatosis and meningiomatosis. Familial meningiomatosis, if it truly exists, is very rare, and familial schwannoma tosis is un common.