Tumor-host interactions as prognostic factors in the histologic assessment of carcinomas.

Many of these observations appear to define a reasonable hypothesis. High-grade or poorly differentiated malignant neoplasms have a shorter tumor-doubling time, are less cohesive, often with irregular borders, and tend to invade by small aggregates and individual tumor cells. The observation of the pattern of invasion provides considerable information on the aggressiveness of the neoplasm. The pattern of invasion appears to correlate with tumor cell cohesiveness, motility, loss of contact inhibition, excretion of enzymes, and other factors associated with aggressiveness in experimental models. It is clear that the pattern of tumor-host interaction indirectly reflects many of these parameters and provides major clues to the biologic potential of human carcinomas. These observations should be used to supplement the histologic and cytologic features commonly used to derive a tumor grade. Aggressive tumors are usually larger and are associated with a greater blood supply. Vascular invasion is more common in this situation and large veins may be invaded by tumor by intravascular growth. Penetration of small lymphatic and blood vessels is associated with a poor prognosis and involvement of large veins with intravascular extensions of tumor have the potential of releasing tumor cell aggregates or emboli into the venous circulation. These large tumor cell aggregates have been demonstrated to be associated with a higher efficiency of metastasis formation and infer a poorer prognosis. Why have I bothered with all this detail about the occurrence of circulating tumor cells and their relation to the development of metastases? It must be stressed that many malignant cells are being released into the circulation of cancer patients and few, if any, ever successfully complete the complex sequence leading to a metastatic focus. This has been termed "metastatic inefficiency." Other investigators have referred to the unique cells that have mastered the intricate sequence of steps required to establish metastases as winners of the metastases decathlon. The observations of vascular (lymphatic or blood) invasion in random tissue sections and their relation to patient prognosis can be best explained by our basic knowledge of cancer biology. The finding of occasional small aggregates of single tumor cells in vascular spaces statistically implies that a considerable number of cells must be entering the vascular compartment.(ABSTRACT TRUNCATED AT 400 WORDS)