If we then put aside completely the conceptual frame of contemporary oncology with all its interpretative variables of genetic, immuncological and toxicological character, what is left as the only logical, practicable way is the domain of the infectious diseases, to be seen and reconsidered with different eyes that has been the case so far.
Two considerations support such a conclusion. One is of a historical nature, and the other is of an epidemiological nature. The former derives from the fact that, in the therapeutical approach to the patient, the improvement in quality, that is the possibility of a real cure for the patient, has been determined almost exclusively by the development of microbiology. The latter derives from the analysis of life expectancy that has taken place in the last decades which, since it is associated with an inevitable change of the sthenicity of individuals, can be hypothesised as a determining factor in the development atypical infectious pathologies.
In order to find the possible carcinogenic ens morbi on the horizon of microbiology, it appears useful to return to the basic taxonomical concepts of biology, where we can see, incidentally, the existence of a noticeable amount of indecision and indetermination.
Already in the last century, a German biologist, Ernest Haeckele (1834-1919), departing from the Linnaeian concept that makes for two great kingdoms of living things (vegetable and animal) denounced the difficulties of categorising all those microscopic organisms which, because of their characteristics and properties, could not be attributed to either the vegetable or animal kingdom. For these organisms, he proposed a third kingdom, called Protists.
“This vast and complex world includes a range of entities beginning with those that have sub-cellular structure — existing at the limits of life — such as viroids and viruses, moving through the mycoplasms, to finally, organisms of greater organisation: bacteria, actinomycetes, mixomycetes, fungi, protozoa, and perhaps even some microscopic algae.” (2).
The common element of these organisms is the feeding system, which, being implemented (with very few exceptions) by direct absorption of soluble organic compounds, differentiates them both from animals and vegetables. Animals also feed as above, but especially by ingesting solid organic materials that are then transformed through the digestive process. Vegetables are capable, by utilising mineral compounds and light energy, to feed by synthesising the organic substances.
The contemporary tendency of biologists is to once again pick up, though in a more sophisticated way, the concept of the third kingdom. One goes even further, however, arguing that within that kingdom, fungi must be classified in a distinct category.
O. Verona (3) says that if we put multicellular organisms provided with photosynthetic capabilities (plants) in the first kingdom, and the organisms not provided with photosynthetic pigmentation (animals) in the second kingdom, and organisms from both these kingdoms are made of cells provided with a distinct nucleus (eukaryotes); and, furthermore, if we put in another kingdom (protists) those monocellular organisms that have no chlorophyll and have cells that are without a distinct nucleus (prokaryotes), the fungi can well have their own kingdom because of the absence of photosynthetic pigmentation, the ability to be mono-cellular, and multi-cellular, and, finally, their possession of a distinct nucleus.
Additionally, fungi possess a property that is strange when compared to all other micro-organisms: the ability to have a basic microscopic structure (hypha) with a simultaneous tendency to grow to remarkable dimensions (up to several kilograms), keeping unchanged the capacity to adapt and reproduce at any size.
From this point of view, therefore, fungi cannot be considered true organisms, but cellular aggregates sui generiswith an organismic behaviour, since each cell maintains its survival and reproductive potential intact regardless of the structure in which it exists.
It is therefore clear how difficult it is to identify all the biological processes in such complex living realities. In fact, even today, there are huge voids and taxonomical approximations in mycology.