Fundamental Differences from Leukemias
Although both pathologies belong to neoplasms of the hematopoietic and immune systems, there is a strict boundary between them. The main criterion is the localization of the primary malignant transformation.
In lymphomas, lymphocyte transformation never occurs in the bone marrow. The pathological process starts in peripheral structures:
- In the tissue of lymph nodes.
- In the lymphoid tissue of various internal organs.
- In other tissues and organs (a characteristic example is plasmacytoma, where the tumor substrate is located in bones).
The second crucial difference lies in the nature of circulation: initially, tumor cells do not circulate in the peripheral blood. A solid, dense tissue mass is formed.
Nevertheless, as the disease progresses, practically all lymphomas acquire the ability to disseminate. This process is called leukemization — malignant cells breach barriers, enter the systemic circulation, and secondarily seed the bone marrow. An important tenet of pathological anatomy: a lymphoma can acquire features of leukemia (leukemize), but the reverse transformation of leukemia into lymphoma is fundamentally impossible.
Pathogenesis and Clinical Manifestations
The development of lymphoma is accompanied by the uncontrolled proliferation of lymphoid tissue, forming a mass lesion. This directly determines the leading clinical sign — compression syndrome.
Enlarging lymph node conglomerates compress neighboring anatomical structures. A typical and dangerous manifestation of such growth is the compression of major vessels, such as the development of superior or inferior vena cava syndrome, which leads to severe hemodynamic disorders.
Since the tumor originates from the immune system, its normal function suffers critically. Severe systemic failures occur:
- Immunodeficiency — the inability of the body to respond adequately to infections.
- Autoimmunization — the paradoxical aggression of surviving or altered immune cells against the body's own healthy tissues.
Etiology and Approaches to Classification
Background conditions play a significant role in the onset of lymphomas. It has been proven that against the background of both congenital and acquired immunodeficiency states, the risk of developing Epstein–Barr virus (EBV)-associated lymphomas increases manifold.
Globally, all lymphomas are traditionally divided into two large branches:
- Hodgkin disease (also known as lymphogranulomatosis).
- Non-Hodgkin lymphomas.
The modern classification of tumors of the hematopoietic and lymphoid tissues, proposed by the World Health Organization (WHO), is based on the histogenetic principle. To accurately determine the type of neoplasm, pathomorphologists require a comprehensive evaluation. A combination of four parameters is taken into account:
- Cytomorphological features (the structure of the cells themselves).
- Immunophenotypic markers (proteins on the surface and inside cells).
- Genetic anomalies (chromosomal mutations).
- Clinical picture of the disease.
According to this approach, all hemoblastoses are divided into main types depending on the progenitor cell: myeloid, lymphoid, histiocytic, and tumors arising from mast cells.