Untersuchungen zur Ultrastruktur und Atiologie der Mastzellentumoren des Hundes

Abstract

A precise electron microscopical distinction between so-called mature and immature mast cell tumours is possible. In immature mast cell tumours, the neoplastic cells contain granules in various phases of development, well-developed ergastoplasm, many free ribosomes, extended Golgi apparatus, complex cytoplasmic membranes, and nuclei with folded nuclear membranes, hypertrophic nucleoli, and finely dispersed chromatin. In mature mast cell tumours, the neoplastic cells have scarce ergastoplasm, fewer free ribosomes, a small Golgi apparatus, some cytoplasmic protrusions, and nuclei with predominantly heterochromatin and only a few folds of the nuclear membrane; the cytoplasmic granules are electron-dense and amorphous or reticular or granular or contain membranous structures. The mature neoplastic cells resemble normal tissue mast cells. In the genesis of granules five phases of maturation can be distinguished. The release of substrate may result from dissolution of granules. In experimental degranulation the release of whole granules may be the immediate result of a relatively strong stress and interference with the cell structure. The intranuclear virus-like structures observed (a small virus containing DNA?) are discussed as a possible oncogenic agent.

Ultrastructural characteristics of mast cells from a canine mastocytoma maintained in vitro*

“…Granule morphology in the cultured tumor cell was similar to that reported by Weiss et al (1968) and Christensen et al (1963) who studied the ultrastrueture of the mastoeytoma via biopsy. However, the highly organized, coiled and laminated structures characteristic of normal tissue mast cell granules (Weinstock & Albright 1967, Barnett 1974 were not observed in the cultured cells of this experiment.…”

“…As the tumor cells in this experiment were initially very aetive, doubling the eell population every 4 to 5 days, the mierotubules might be residual from this phase of cell mitosis. Reports from previous ultrastructural studies of the itt vivo mast cell associated with canine or murine mastocytoma have not mentioned the presence of mierotubules (Bloom 1963, Penelli et al 1964, Weiss et al 1968). It appears, therefore, that the presence of this structure is induced by the in vitro environment.…”

Caine Intestinal Carcinoids

“…Neoplastic canine mast cells have a similar ultrastructural appearance [3; personal observations]. The rough endoplasmic reticulum in poorly differentiated mast cell tumors, however, has been reported to be more extensive [35]. The ultrastructure of mast cells is, therefore, inconsistent with the morphology of the cells in these neoplasms.…”