[On formal genesis of crystalline inclusions in oligodendroglioma (author's transl)]

Cytoplasmic Crystalline Inclusions in a Anaplastic Oligoastrocytoma

A 41-year-old male presented with an ill-demarcated mass involving the left fronto-temporal lobe and the basal ganglia. Light microscopically the tumor was diagnosed as an anaplastic oligoastrocytoma. Electron microscopy revealed several cytoplasmic crystalline inclusions in tumor cells of oligodendroglial lineage. No crystalline inclusions were membrane bound. The morphologic features with unique ultrastructural findings are presented.

Crystals in an oligodendroglioma: an optical, histochemical, and ultrastructural study

The report describes an oligodendroglioma that was examined in four biopsies and contained a large number of intracytoplasmic crystals. The crystals appeared in neoplastic cells with eosinophilic cytoplasms and eccentric nuclei. They were positive to periodic acid-Schiff stain and resistant to diastase. A lysosomal genesis of the crystals is proposed on the basis of a transition observed between lysosomal bodies with lipid droplets and those with crystalloid electron-dense structures. The morphologic and histochemical features of these crystals are compared to those in other tumors, lesions, and nonneoplastic cells.

The ultrastructure of oligodendrogliomas

Seven Oligodendrogliomas (2 with uniform cell type, 4 with cellular or tissue variability, and 1 with glioblastomatous changes) were examined ultrastructurally. The tumor cells were of two principal types with morphologic transitions between the two main types. The two principal cell types were identified as type 1 (undifferentiated) and type 2 (differentiated) on the basis of the number of anaplastic cells in an individual tumor and on the observations of Mori and Leblond (21) on non-neoplastic oligodendrocytes. Most of the tumor cells in all tumor exhibited similar histologic and ultrastructural characteristics including their arrangement and their tendency to form cytoplasmic processes which sometimes formed short stacks. These features were also recognizable in the glioblastomatous example and confirmed the presence of an oligodendroglial component. In addition to these characteristics, an increase in size and number of mitochondria, abundant intracytoplasmic structures, microtubules were regularly present in virtually all tumor cells. Cells rich in cytoplasmic filaments were present. These were identified as reactive astrocytes or as oligodendroglial tumor cells. Thus neither cytoplasmic filaments nor microtubules appear to be specific morphological markers for oligodendroglia or astrocytes; only the predominance of one of these structures permits cytogenetic identifications. The cytologic characteristics are not specific morphologic markers; however, recognition of their presence provides important diagnostic information.

Ultrastructure of oligodendrogliomas

The study of 18 oligodendrogliomas shows a number of characteristics which indicate a common hypothelial stem cell. The main cytologic characteristics are: a) high number of mitochondria, frequently atypical; b) polygonal crystalline structures in the cytoplasm in most of the tumors studied, and c) cytoplasmic microtubuli. None of these characteristics can be considered as pathognomic for the oligodendrogliomas. However, rows of folding cell processes represent a fundamental structural principle of all oligodendrogliomas and since they have not been found in any other brain tumor and may be regarded as an inherent and specific characteristic of the oligodendroglial group.

Definition of a cell clone with astroglial characteristics derived from a chemically induced rabbit brain glioma

Three-month-old rabbits were started on a fortnightly schedule of intravenous injections of N-methyl-N-nitrosourea. All but two of the central nervous system tumors induced in this manner were propagated in culture as permanent cell lines. On the 76RB-G-414-H line established from a grade 2 astrocytoma of this series of neoplasms, a cloning procedure was carried out using a laser microbeam. The clonal line originated in this way has been maintained in long-term culture and given the 76/RB-G-414-H-C designation. The cells of the clone display invariably a bipolar or multipolar configuration with long processes. Intermediate filaments are common and even abundant in some cells. Positivity for S-100 and GFA proteins is a regular finding in these cells. In addition, dibutyryl cyclic adenosine monophosphate treatment reduces cell division and stimulates cell process formation of these cells. Thus, it appears that we succeeded in establishing in vitro and maintaining in long-term culture a clone of tumor cells with astrocytic characteristics.