Malignant haemangiopericytoma of lung: a cell culture and ultrastructural study.

Malignant haemangiopericytoma was grown in vitro to assess the histogenesis of the tumour. Disaggregated tumour cells maintained in serum-supplemented Waymouth's MB 752/1 medium showed monolayers of homogeneous spindle cells. Post-confluent cultures exhibited hillocks or plaques of multilayer growth within which considerable amount of basal lamina-like material and fibrillar matrix were present between cells. Delicate basal laminae were also expressed on cell surfaces facing matrix material. Other consistent features were attenuated cytoplasmic processes, desmosome-like junctions, abnormal mitochondria and a paucity of intracellular filaments. The three-dimensional organization of tumour cells with concomitant expression of differentiated phenotype in vitro has significant implications on the cell of origin and differentiation process of haemangiopericytoma.