Intracisternal crystalline arrays of coated parallel tubules in cells of a human osteosarcoma

Abstract

Crystalline arrays of coated parallel tubules (CPT) were observed by electron microscopy within dilated cisternae of the rough endoplasmic reticulum of pleomorphic mononuclear cells in a human osteosarcoma. The wall of the peculiar intracisternal tubules consisted of an electron-dense thin membrane-like envelope which appeared to be composed of granular subunits. The electron-lucent tubular core together with the limiting envelope was approximately 15 nm in diameter. A coat of fuzzy material, approximately 10 nm thick, tightly surrounded the membrane-like wall of the tubules. Cross sections of accumulations of CPT showed the tubules to be arranged in a hexagonal crystalline array. The nature and significance of the intracisternal CPT are unknown.

Case Report: Microtubular Aggregates within the Rough Endoplasmic Reticulum of Embryonal Rhabdomyosarcoma Cells: A Case Report

“…Similar findings have also been described in many cases of extraskeletal myxoid chondrosarcoma [ 2± 6] and rarely in osteosarcoma [7] and chordoma [8,9]. MA in rER are considered to be characteristic ultrastructural features of extraskeletal myxoid chondrosarcoma, though they are not specific.…”

“…Therefore, these tumor cells are committed to skeletal muscle differentiation. MA in rER have been described in various nonepithelial tumors, including malignant melanoma [1], skeletal and extraskeletal myxoid chondrosarcoma [2± 6], osteosarcoma [7], and chordoma of either chondroid or nonchondroid conventional type [8,9]. The incidence of extraskeletal myxoid chondrosarcoma with MA in rER is approximately 30± 40% (14 of 41 cases) and MA are considered to be useful diagnostic markers for extraskeletal myxoid chondrosarcoma [12].…”

Extraskeletal myxoid chondrosarcoma: Updated clinicopathological and molecular genetic characteristics

“…The microtubular aggregates are fairly characteristic of EMC (Fig. 3), 28,59,88–92 and they have been described only in limited types of other tumors such as malignant melanoma, 93 osteosarcoma, 94 chordoma, and embryonal rhabdomyosarcoma 95–97 . Although at least one‐third of EMC are assumed to have microtubular aggregates, 17,19,39,89 their physiological function is not clear.…”