K. L. Ho

Colloid cysts of the third ventricle: ultrastructural features are compatible with endodermal derivation.

SummaryThe histogenesis of colloid cyst of the third ventricle remains unsettled. Ultrastructural and immunohistochemical analyses have suggested the following possible origins: (a) neuroepithelium, including paraphysis, ependyma, choroid plexus and tela chorioidea; and (b) endoderm, including respiratory and enteric epithelium. This report describes the ultrastructural features of the lining epithelium in four cases of colloid cyst. Six distinct cell types were recognized: (1) ciliated cells with occasional abnormal cilia; (2) non-ciliated cells with microvilli coated with granulofibrillary material; (3) goblet cells showing discharge of secretory granules; (4) basal cells with prominent tonofilaments and desmosomes; (5) basal-located cells with elongated electron-lucent cytoplasm and scattered membrane-bound dense-core granules (150–350 nm); and (6) small undifferentiated cells with scanty organelles. Junctional complexes were present in the former four cell types but absent in the latter two. The types of epithelial cells and their topographic distribution within the epithelium are both very similar to those of normal respiratory epithelium and to the lining epithelium of intraspinal bronchogenic cyst. The observations made in the present study are compatible with the hypothesis that colloid cysts of the third ventricle originate from the endoderm, most likely the respiratory epithelium.

Neuropathologic findings in thanatophoric dysplasia

SummaryNeuropathologic study of eight cases of thanatophoric dysplasia (dwarfism) reveals developmental abnormalities including hypoplasia of posterior fossa, megalencephaly, cerebral gyral disorganization, hippocampal malformation, neuronal heterotopia, nuclear dysplasia, and abnormal axonal bundles. There are no noticeable differences in CNS abnormalities between thanatophoric dysplasia with and without cloverleaf skull (Kleeblattschädel). The CNS abnormalities, likely the result of abnormal neuronal migration and cytoarchitectonic disarrangement, are apparently not caused by skeletal abnormalities. The observation suggests that CNS abnormalities represent a characteristic and distinct manifestation of thanatophoric dysplasia.

Ultrastructure of cerebellar capillary hemangioblastoma

SummaryConcentric 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.

Histogenesis of sarcomatous component of the gliosarcoma : an ultrastructural study

SummaryThis report describes the ultrastructural findings of the sarcomatous component in five cases of gliosarcoma. The tumor contained a heterogenous population of cells with collagen scattered in the interstitium. Three main cell types were found: histocyte-like cells, fibroblast-like cells and undifferentiated cells. The histocyte-like cells had oval nuclei, short and flat rough endoplasmic reticulum, prominent Golgi apparatus, lysosomes, phagocytic vacuoles, ruffled cytoplasmic membrane with filopodia, segmental basal lamina and occasional intercellular junctions. The fibroblast-like cells had elongated nuclei, prominent cisterns of rough endoplasmic reticulum and microfilaments. The undifferentiated cell cytoplasmic processes suggesting differentiation toward histiocyte-like cell. In addition, intermediate cells, myofibroblasts, multinucleated giant cells and xanthomatous cells were also present. Occasional glial processes were interposed between tumor cells. Some were enclosed by cytoplasmic processes of histocyte-like cells and others engulfed within the cytoplasm. Capillary showed surface infoldings, fenestrations of endothelial cells, thickened basal lamina, occasional pericytes and scattered collagen. Some capillaries were surrounded by aggregating histiocyte-like cells and undifferentiated cells. The present findings suggest that (a) the sarcomatous component in gliosarcoma is likely derived from undifferentiated cells with a broad differentiation into histiocytic, fibroblastic and other cell types, (b) endothelial cells and pericytes may not participate in sarcomatous development, (c) capillaries within the sarcomatous component are of non-gliomatous type, and (d) the histiocyte-like cells are capable of phagocytizing glial elements.

A glioependymal cyst of the cerebellopontine angle

SummaryEpithelial cysts in the subarachnoid space are infrequently reported and appear to be histogenetically heterogenous. This report describes the gross, immunohistochemical and ultrastructural findings of an asymptomatic isolated 3-cm epithelial cyst in the cerebellopontine angle. The cyst wall was composed of an inner glial layer with a luminal ependymal lining and an outer fibrous layer with no external lining cells. The lining ependymal cells had vacuoles, bleb-like protrusions, normal and abnormal cilia, and microvilli, the later were sometimes distended and detached into the lumen. They possessed neither pinocytic vesicles nor a basement membrane. The glial layer contained astrocytes, glial bundles and ependymal cells, often in pairs and forming intercellular lumina with cilia and microvilli. Some single and paired ependymal cells contained abnormal cilia and intracytoplasmic lumina. The blood vessels within the glial layer had elongated tight junctions and were fenestrated. The glial layer was demarcated from the outer fibrous layer by a continuous basement membrane. This cyst appears to have originated from a leptomeningeal neuroglial heterotopia and may represent a continued proliferative growth rather than degenerative change of the heterotopia.

Intraspinal bronchogenic cyst: ultrastructural study of the lining epithelium.

SummaryThis report describes the ultrastructural characters of the lining epithelium of a symptomatic intraspinal bronchogenic cyst at the C5-T2 level of a 21-year-old female. Six distinct cell types were recognized: ciliated cells, non-ciliated cells, and goblet cells that reached the lumen, and basal cells, Kulchitsky cells and undifferentiated cells that were basally located and did not reach the lumen. The microvilli of non-ciliated cells were coated with granulofibrillary material. Discharge of granular contents from goblet cells was noted. Abnormal cilia, particularly compound cilia, were frequent. Complex interdigitations of cytoplasmic membrane with prominent desmosomes were present in the pseudostratified region. Kulchitsky cells contained characteristic membrane-bound dense-core neurosecretory granules. Intraepithelial unmyelinated axons were observed but none were closely associated with Kulchitsky cells. The types of cells forming the lining epithelium of the present cyst and their topographic distribution within the epithelium are very similar to those of the normal tracheobronchial epithelium.

Abnormal cilia in a fourth ventricular ependymoma

SummaryAlthough the luminal surface of the ependymal cells of the human ventricular system is characterized by the presence of cilia with a typical 9+2 arrangement of microtubules, cilia are usually described as sparse or absent in ependymal cells of ependymomas. The incidence of aberrant cilia and structurally abnormal cilia in normal ependymal cells and ependymomal cells has not been documented. This report describes detailed ultrastructural and quantitative studies of cilia of the ependymal cells of a fourth ventricular ependymoma in a 5-year-old boy. Of a total of 267 cilia studied, 50% were located in the extracellular microrosettes, 30% in the intracytoplasmic lumina and 20% in the cytoplasm. Thirty percent of all cilia studied showed structural abnormalities. Those present in the aberrant locations, e.g., intracytoplasmic lumina and in the cytoplasm, had a higher incidence of abnormality. Ciliary abnormalities fell into four majors categories: (1) cilia with abnormal axial microtubules, (2) compound cilia, (3) swollen cilia, and (4) cilia with dynein arm defect. Of these, addition, deletion and disorganization of axonemal microtubules were most common. The present study suggested that ciliary abnormality is common in ependymoma and may represent another example of oncogenetic effect on the ciliogenesis of ciliated epithelium.

Subarachnoid epithelial cyst of the cerebellum

SummaryThis report describes the immunohistochemical and ultrastructural studies of a subarachnoid epithelial cyst of the cerebellum found incidentally at autopsy of a 76-year-old man. The cyst was composed of an inner epithelial layer, a middle connective tissue layer and an outer arachnoid membrane. The epithelial layer was strongly positive for cytokeratin, carcinoembryonic antigen and epithelial membrane antigen, but negative for glial fibrillary acidic protein, S-100 protein, neuron-specific enolase and vimentin. Ultrastructurally, the epithelial layer had four distinct types of cells: ciliated cells, non-ciliated cells with coated microvilli, basal cells with tonofilaments and desmosomes, and cells with dense-core secretory granules (Kulchitsky cells). The latter two types of cells have not been described previously in epithelial cysts of the CNS. The lining epithelium closely resembled the upper respiratory epithelium. The findings suggest that the cyst was of endodermal rather than neuroectodermal origin.

Hirano body in an inflammatory cell of leptomeningeal vessel infected by fungus paecilomyces

SummaryAn intracytoplasmic microfilamentous lattice, ultrastructurally identical to Hirano body, was found in an inflammatory cell within a leptomeningeal vessel wall infected by fungus Paecilomyces javanicus. The structure was well preserved and not associated with phagosomes. This is the first report of Hirano body found in an inflammatory cell at the site of fungal infection. The present finding suggests that the formation of Hirano body is non-specific and not restricted to the cell of the neuro-muscular system.

Crystalloid bodies in skeletal muscle of hypothyroid myopathy

SummaryCrystalloid bodies in skeletal muscle fibers have been described in myopathic and non-myopathic conditions. They have been interpreted as viral, glycogen, protein-glycogen complex, artifacts and of unknown nature. This report described similar crystalloid bodies in the postmortem muscle samples of two patients with hypothyroid myopathy. The crystalloid bodies were preferentially located in the I band and Z line region and in the subsarcolemmal region closely associated with lipofuscin. Some were present within basophilic bodies. They were formed by parallel filaments of 6–10 nm beaded periodically by electron-dense particles of 10–18 nm in a lattice, hexagonal or parallel-ripple pattern. Merging of filaments of crystalloid bodies into actin filaments of the I band was noted. The electron-dense particles stained strongly with periodic acid-thiocarbohydrazide-silver proteinate method for polysaccharides and were unaffected or partially digested by diastase treatment on the ultrathin sections. The filamentous component was neither stained for polysaccharides nor digested by diastase treatment. It is suggested that crystalloid bodies of muscle fibers are composed of two distinct subunits with particles of glycogen complex attached to filaments of unknown nature.