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Cells derived from Kaposi's sarcoma (KS) were propagated in vitro using conditions which resulted in elimination of contaminating fibroblasts and the emergence of homogeneous cell populations which morphologically resembled smooth muscle cells and had neoplastic characteristics. In long-term culture, they differentiated into large ribbon-like cells with longitudinal fibrillarity of their cytoplasm. These fibrils stained red by Masson trichrome staining, and were reactive with antibodies to desmin. Dense bodies typical of myoblasts were observed in some cells by electron microscopy. The cells did not form capillary structures like endothelial cells, they lacked Weible-Palade bodies, and did not express the blood-clotting Factor VIII-related antigen or receptors for the lectin Ulex europaeus agglutinin I. They did express four other antigens, however, in common with endothelial cells. The cells did not form tumors in athymic nude mice; however, they formed colonies in soft agar, manifested tumor-like growth on muscle organ cultures, and were invasive in an artificial basement membrane invasion assay. The results indicate that a component of KS is closely related to leiomyoblasts and and has neoplastic properties.

Cyclophosphamide (CPM) was first synthesized in 1958 by Arnold and Bourseaux as part of a program to develop new anticancer agents with fewer side effects and greater efficacy than those in existence. There are now many reports of good response rates obtained with CPM in patients with both hematological and solid malignant conditions, and it has been widely accepted as an important component of multi-drug regimens. What remains to be proven, however, is whether CPM significantly improves survival expectancy when used either alone or in combination with other agents. It should be remembered that evidence of efficacy as a single agent in terms of response rate or even complete remission may not be translated into improved survival when that agent is incorporated into a multi-drug regimen. Before a chemotherapeutic agent is evaluated as part of a multi-drug regimen there should be adequate evidence of efficacy against the relevant tumor. In addition, the agent must be used at a dosage that has been established as adequate. Despite these safeguards, it is not necessarily true that the addition of the drug either alone or as part of a multi-drug regimen will improve survival. Further use of the agent alone or in combination would then be illogical, just as it would be to use agents that have been shown to be ineffective, or to use an agent at too low a dose. The purpose of this article is to review the accumulated experience with CPM in both adult and pediatric oncology in the treatment of solid tumors with the above considerations in mind.