Secondary Primary Cancers

Neoplasms are considered either as spontaneous or induced (experimental or iatrogenic). Spontaneous multiple primary neoplasms exhibit an intra- and interspecies variety (Chapter 6/Chapters 5 & 6/Volume III). But the reality is more complex. Spontaneous neoplasms, as found for example in the wild, may be produced by single types of causes whereas human neoplasms, with the diversity of our active life, may be more often produced by the chain reaction of different agents. In experimentally induced neoplasms, single agents are generally excessively applied; this does not happen in free-living organisms, including man. It does not matter whether a tumor develops spontaneously or experimentally, because in neoplastic development the central point of interest is the transformation of normal into malignant cells preceded and followed by certain host-tumor interactions, as previously described (see Volumes III and IV). In a certain sense, iatrogenic induction or spread of neoplasms may appear by single modality.