Pericellular deposition of basement membrane material in myxoid meningioma: immunohistochemical evidence for unbalanced production of type IV collagen and laminin.

Myxoid meningioma seen in a 25-year-old man is presented. Histologically, Leu 7-positive meningotheliomatous tumor cells were embedded in the alcianophilic myxoid matrix. Characteristically, eosinophilic granular deposition was detected around the tumor cells and the boundary of tumor cells was not clearly defined. The pericellular deposits revealed the nature of the basement membrane with positive reactions by periodic acid-Schiff (PAS) sequence and immunostaining for type IV collagen, which is the major structural component of basement membrane. However, laminin, which is a non-collagenous glycoprotein of the basement membrane, was undetectable, and silver was not impregnated. Similar abnormal deposition of PAS-positive basement membrane-like material was observed in the myxoid stroma of a microcystic meningioma among 72 meningiomas additionally examined. The significance of the discrepant localization of immunoreactive type IV collagen and laminin is discussed.