Ultrastructure of cerebellar capillary hemangioblastoma. V. Large pinocytic vacuolar bodies (megalopinocytic vesicles) in endothelial cells

Ultrastructure of cerebellar capillary hemangioblastoma. VI. Concentric lamellar bodies of endoplasmic reticulum in stromal cells

Concentric lamellar bodies of endoplasmic reticulum (CLB) were found in the stromal cells of all five cases of cerebellar capillary hemangioblastoma studied ultrastructurally. CLB were often present in the stromal cells with voluminous loose cytoplasm, particularly those close to the capillaries. They were rarely seen in small stromal cells with abundant organelles and stromal cells distended by large lipid droplets. Small lipid droplets were usually present in the center or in the vicinity of CLB. Vesiculation and vacuolization of the lamellar arrays of CLB were common. Some vacuolized CLB were transformed into large, varying-shaped, multilocular bodies. Some stromal cells were markedly distended by numerous large vacuoles derived from CLB. Granulo-fibrillary material was frequently present in the vacuolized lamellae. Discharge of vacuoles into the interstitial space was observed. It is suggested that CLB is one of the characteristic ultrastructural features of the stromal cells. They may represent a special type of hyperplasia of the endoplasmic reticulum, but their functional significance is not known.