Rudimentary meningocele of the scalp.

A rudimentary meningocele, a variant of primary cutaneous meningioma, was seen on the scalp of a 9-month-old Japanese boy. Clinically, the lesion on the left parietal area was round, about 1.6 cm in diameter, alopecic, and slightly elevated. Histologically, the lesion, located from the dermis to the subcutis, consisted of scattered foci of meningothelial cells, an anastomosing network of empty spaces with psammoma bodies and collagen bodies, and small vessels. Immunohistochemically, the meningothelial cells were positive for vimentin and desmin. Ultrastructurally, they had elongated cytoplasmic processes, intermediate filaments in the cytoplasm, and desmosomal junctions.