Expression of the stem cell marker CD133 in malignant meningioma.

The stem cell marker CD133 has been sporadically investigated in meningioma, but because of the rarity of malignant meningioma (WHO grade III), only 7 malignant meningioma specimens have been included in previous studies. We investigated CD133 expression using the AC133 antibody clone in a consecutive cohort of 38 malignant meningiomas. Our results showed few, small CD133-positive hot spots with a pattern dominated by membranous staining and capping of the proteins without any nuclear CD133 staining in 30 of the 38 tumors. We could not corroborate spatial co-expression of hot spots with the proliferative marker, Ki-67, and CD133 hot spots in adjacent slides, nor did we find differences between Ki-67 expression in CD133-negative and -positive tumor specimens (Fisher's exact test: p = 0.69). CD13-positive niches represented only 0 - 1% of meningioma cells in most of the malignant meningioma, while CD133-positive cells were undetectable in 21% of the whole-section tumor samples. We found stem cell niches in 79% of malignant meningioma specimens in our cohort.