Multiple meningiomas. Report of nine cases.

Multiple meningiomas are a seldom encountered neoplasm. Most authors report an incidence ranging from 1 to 3% of all meningiomas. The routine use of CT has resolved diagnostic problems involved with multiple meningiomas; nevertheless, they still present several nosologic problems. In fact, it may be difficult to differentiate "true multiple meningiomas", defined as a distinct entity by Cushing in 1938, from simple recurrences or the special variant (forme fruste) of von Recklinghausen's disease. Our report deals with nine cases of multiple meningiomas selected from a series of 372 meningiomas operated from 1968 to 1981 at our hospital. Cases were divided into a) multiple simultaneous meningiomas (five cases), b) multiple meningiomas successively detected at different localizations (two cases), and c) multiple meningiomas associated with neurofibromatosis (two cases). Only five of these nine cases, four from the first group and one from the second, were true multiple meningiomas. Pathogenetic factors related to true multiple meningiomas are discussed in relation to the literature reports. However, the different hypotheses proposed do not offer a definite explanation of the multicentricity of these tumours.