Foci of amorphous/granulofilamentous matrix in the extracellular domain of tumours: a study of 34 cases. 1. Ultrastructural characterisation.

Abstract

The distribution and the appearance of foci of extracellular amorphous/granulofilamentous material (FEAM) in 34 human tumours are described. FEAM were rounded to oval, or more elongated or irregular elements of discretely delineated dense material lying in the extracellular space of tumours. They varied in size and abundance, sometimes coalescing into more extensive areas of dense material. At high magnification, FEAM exhibited a granular and finely filamentous substructure. Variations in the electron-density of FEAM were noted. Some FEAM were found associated with the surfaces of tumour cells, on occasion with subplasmalemmal linear densities. FEAM was also sometimes associated with matrix filaments, often collagen. Material of similar substructure and density was also associated with some vessels. FEAM were mostly found in tumours showing mesenchymal differentiation. The nature and origin of FEAM is discussed.