[Individuality of malignant neoplasms]

The article concerns the implication of the tumor cell heterogeneity, which is caused by the genetic instability of tumor cells. Thereby, within a given tumor, subpopulations with differing marker profiles may appear in a very irregular fashion. For instance, some populations may show criteria which under normal circumstances are mutually exclusive. In so far, the tumor cell heterogeneity can be viewed as responsible for the fact that tumor classifications are never scientific classifications which are defined by reliable and stable criteria. Furthermore, the tumor cell heterogeneity must be born in mind when malignant tumors are graded. Grading provides usually only statistical results which must not necessarily be valid for the individual case. It is concluded that malignant neoplasias should be considered much more individually if we were to take their biologic behaviour properly into account. This, however, bears considerable difficulties, especially with respect to diagnostic and therapeutic conclusions.