Repeated multifocal recurrence of grade I, grade II, and grade III meningiomas: regional multicentricity (primary new growth) or metastases?

In this study 48 patients with histologic grade I and 41 with grade II/III meningiomas were reviewed retrospectively for the occurrence of multifocal tumor masses in relation to recurrence. Regional multicentric tumor masses were increasingly seen in progressive disease with repeated recurrence and occurred significantly more frequently in grade II/III compared to grade I meningiomas. Small microscopic tumor extensions along the subdural space around the tumor bulk, defined as tumor spurs, could be documented as an alternative form of multifocal disease. The occurrence of these spurs was associated with recurrence. In nearly all cases the multifocal disease was limited to the vicinity of the primary or previous tumor site. In three patients with grade III meningiomas however, at recurrence distant tumors could be found. These were interpreted as drop, cerebrospinal fluid and hematogenic metastases, respectively. In these three cases tumor spurs were documented in previous operations. It is concluded that not only primary new growth in a tumor that virtually from the beginning already has a regional multifocal origin, but also the spread of tumor cells along the subdural space forming tumor spurs, as well as distant metastases, plays an important role in recurrent meningioma.