Intracellular collagen fibrils in human sarcomas

Intracellular collagen was detected by electron microscopy in 14 sarcomas, including 6 osteogenic sarcomas, 3 liposarcomas, 3 malignant fibrous histiocytomas, 1 pleomorphic rhabdomyosarcoma, and 1 childhood rhabdomyosarcoma. It was contained in not only the fibroblastic cells, but also in the osteoblastic, lipoblastic, myofibroblastic, and primitive cells of the various tumors. The banded intracellular collagen fibrils were observed in large phagocytic vesicles and in smaller membrane-bound vesicles, which also appeared to fuse with lysosomes. Residual banding could be seen as well in many such phagolysosomes. Banded collagen was also noted in a primary explant in tissue culture. These findings suggest that the configurations of intracellular collagen seen are parts of a continuum of a secondary pathway of collagen degradation in mesenchymal tissue and that pathway is one factor indicating a close interrelationship between these sarcomas.