Particle—lamella complex and lamellar crystalloid in human meningioma

Abstract

Two characteristic crystalloids were evident in the cytoplasm of human meningioma. The first type, tentatively designated as a particle—lamella complex, was shown as a slender and straight rod often with tapering ends, and usually composed of closely packed parallel arrays of dense lamellae which were closely associated with ribosome-like particles. The individual lamellae were 80–170 in thickness and aligned in the long axis of the crystalloid. The ribosome-like particles were arranged linearly in the interlamellar spaces at about 200–450 intervals. The particle layer was not composed of the ribosome-like particles alone, but often replaced by the lamellar structure. In the same way, the lamellar layer partly consisted of the ribosome-like particles. Thus, the particle layer and the lamellar layer were oriented in an alternating manner. In addition, the ribosome-like particles were often accumulated closely along the particle—lamella complex. The second type of crystalloid, a lamellar crystalloid, consisted of parallel lamellae which were oriented regularly at about 400 intervals. Usually, no ribosome-like particles were evident in the interlamellar spaces. However, a few lamellar crystalloids showed the ribosome-like particles which were oriented linearly for a short distance in the interlamellar spaces or along the outermost lamella, and revealed a close morphological relation to the particle—lamella complex. It might be suggested that the lamellar crystalloid was formed by the activity of the ribosome-like particles from the particle—lamella complex, or vice versa.