Volumetric analysis of a rhabdoid meningioma during preoperative follow-up. A case report.

The authors describe a case of rhabdoid meningioma (RM) in a 17-year-old boy that was determined by measuring the tumor volume during preoperative follow-up. The volume of the tumor located in the left occipital lobe, was measured every 1-5 months, using an image analysis software. The tumor volume doubling time (Td) ranged from 1.0 to 4.9 years in the first 11 months, but became 0.3 years in the last two months. The tumor grew rapidly in the last two months at which time surgery was performed. Pathological examination of the surgical specimen showed that the tumor contained rhabdoid cells (RCs). RCs were heterogeneously distributed in the tumor admixed with spindle-shaped cells. The areas where RCs were predominant had malignant histological features, with necrosis and high proliferation indices, whereas the areas with few RCs lacked the malignant features. The tumor grew slowly in the initial phase, possibly because components with low proliferation rates occupied most of the tumor. The tumor began to grow rapidly when the malignant component containing abundant RCs became predominant. To the authors' knowledge, this is the first report monitoring the volumetric change of RM periodically. Our investigation indicated that volumetric analysis is useful to decide surgical intervention of the meningiomas with potential malignancy.