This retrospective study analyzed 9 LVM cases for which gross total removal was achieved. Expression of the ependymal cell marker (Forkhead Box J1 [FoxJ1]) was histopathologically evaluated. The distribution of quiescent and activated fibroblasts was also analyzed using anti-fibroblast-specific protein-1 (FSP1)/S100A4 antibody and anti-α-smooth muscle actin (αSMA) antibody, respectively. The control group was 5 cases with primary convexity meningioma for which Simpson grade I removal was achieved.
Small LVMs (≤30 mm) were covered by a FoxJ1-positive(+) ependymal cell monolayer; no αSMA(+) cells were detected in the tumor; and a thick membrane capsule was not observed. None of the convexity meningiomas showed FoxJ1(+) cells. Large LVMs (>30 mm) had thick membrane capsules without an ependymal cell monolayer, which resembled dura mater. The FSP1/S100A4(+) and αSM(+) cells were clearly concentrated in the peripheral area just below the thick dura mater-like membrane capsules.
This study found an association between activated fibroblasts and dura mater-like membrane capsules in LVMs. The characteristics of membranous structure in LVMs may differ depending on tumor size.