Lymphoma is a group of malignant haematological diseases of lymphatic tissue characterised by malignant transformation of lymphoid cells;

– the precursors of malignant stem cells are pluripotent or unipotent stem cells of lymphopoiesis located in the red marrow;

– the first stage (initiation) of the “birth” of a malignant stem cell takes place in the red marrow, the second stage (promotion) in the location of the primary malignant focus;

– the basis of a malignant stem cell “birth” is a block of differentiation and transformation of a pluripotent or unipotent stem cell of lymphopoiesis;

– the mechanism of a malignant stem cell “birth” is the genotype and epigenetic changes of a pluripotent or unipotent stem cell of lymphopoiesis following the carcinogenic impact;

– the malignant process starts from the “birth” of one malignant stem cell, which then forms a clone of malignant cells;

– the malignant process is manifested through forming the primary malignant focus located in the lymph nodes (nodal involvement) or in any other organs and tissues (extra nodal involvement);

– the malignant process is developed by lymphogenous spread in the host body, sometimes cells of lymphoma are detected in the blood, but usually they tend to form thick tumours in the lymphatic system or in the internal organs (liver, stomach, nervous system or in other places);

– the malignant process impacts haemopoiesis, homeostasis, immunity etc.

Solid Tumours are the largest in quantity, heterogeneous group of malignant diseases, which develop through multi-stage malignant transformation of a normal proliferating somatic cell into a malignant stem cell:

– the origins of malignant cells are not known, as the precursor of the malignant stem cells is not known. It is supposed that the precursors are normal somatic proliferating cells – cambial cells, which are located in the area of the crypts’ floor, glands’ neck, periosteum and perichondrium, along the blood vessels’ flow and also in the area of intense restorative proliferation;

– it is not known where and how both stages (initiation and promotion) of the “birth” of a malignant stem cell take place. It is supposed, in the area of intensive proliferation of cells;

– also it is not known what process underlies the “birth” of a malignant stem cell. It is supposed that a normal somatic proliferating cell transforms into the malignant stem cell;

– the mechanism of the “birth” of a malignant stem cell is not known. It is supposed that following the carcinogenic impact the genotype and epigenetic changes of a normal proliferating somatic cell take place, and these are a launching mechanism for its transformation into the malignant stem cell;

– a malignant focus starts with the “birth” of one malignant stem cell (in 80% cases), two or more malignant stem cells (20%), which then form a clone of malignant cells;

– the malignant process is manifested through forming the primary malignant focus, which can be located in different organs and tissues, and it increases by proliferation of cells, appositional and invasive growth;

– the malignant process is developed by the haematogenous and lymphogenous spread in the host body while forming the secondary foci – metastases;

– the malignant process impacts haemopoiesis, homeostasis, immunity etc.

Thus, the contemporary notions:

1. The difference between haemoblastosis (leucosis and lymphoma) on the one hand and solid tumours on the other, is in the mechanism of the “birth” of a malignant stem cell;

– in the case of haemoblastosis, following the carcinogenic impact the genotype and epigenetic changes of a pluripotent or unipotent stem cell of myelo- or lymphopoiesis, a block of differentiation and its transformation into a malignant stem cell take place;

– it is supposed that in the case of solid tumours, following the carcinogenic impact genotype and epigenetic changes of a normal proliferating somatic cell take place, which are a launching mechanism for its transformation into a malignant stem cell.

2. The difference between leucosis on the one hand and lymphoma and solid tumours on the other, is in the manifestation of the malignant process:

– in the case of leucosis, the disease manifests itself by the affection of the red marrow, but the primary malignant focus is not formed. The “birth” of a malignant stem cell requires 2-4 genotype alterations of the nuclear DNA of a pluripotent or unipotent stem cell of myelo- or lymphopoiesis. Epigenetic alterations are of secondary importance, that is why changes in the living conditions and microenvironment of the precursor are not a prerequisite;