Ultrastructure of osteogenic sarcoma

Abstract

An electron microscopic examination of osteogenic sarcoma tissue revealed that the tumor cells resembled normal osteoblasts. The cells had a very thin plasma membrane and some cell processes, but micropinocytotic vesicles were rarely seen. Mitochondria were scanty but frequently enlarged and/or deformed in various ways. Golgi complex and rough endoplasmic reticulum were abundant, and the cisternae of the rough endoplasmic reticulum were often distended—at times forming large lakes. The nuclei were frequently markedly crenated or indented, and nucleopores were prominent. The matrix was composed of fibrils and fibers set in a medium density matrix. Calcification was observed in some areas of the matrix. This study supports the widely held idea that osteosarcoma is a tumor of bone-forming cells, and that well-differentiated examples of this tumor (osteogenic sarcoma) are capable of forming osteoid and bone.