Main differences between tumor tissue and normal tissue
Any neoplasm fundamentally differs from healthy body tissues by a number of unique biological properties. These differences determine the entire severity of the pathological process:
- Connection with genome alterations. The root cause of tumor growth always lies in damage to the cellular genetic apparatus. In the vast majority of cases, somatic mutations are to blame. Germline mutations are significantly less common (in hereditary or familial tumor syndromes).
- Autonomous and uncontrolled growth. Cell division is no longer governed by the normal regulatory signals of the host organism. The tumor obeys exclusively its own autonomous regulation, established by the pathological cells themselves and the supporting stroma.
- Profound disruption of the cell cycle and differentiation. There is a pronounced imbalance between proliferation (cell multiplication) and cell death. Pathological mitotic figures are frequently detected under the microscope.
- Pathology of apoptosis. Programmed cell death in neoplasms is incomplete and characterized by relative insufficiency.
- Growth stimulation via cell death. This is one of the most paradoxical mechanisms: the death of tumor cells does not stop but rather stimulates further growth of the neoplasm. During incomplete apoptosis, disintegrating apoptotic bodies release specific mitogenetic factors that force neighboring cells to actively divide.
Types of tumors and their clinical behavior
In pathological anatomy, all neoplasms are conventionally divided into three major groups. This classification is based on four key criteria: the degree of maturity of cellular elements, the rate and pattern of growth, the ability to metastasize, and the tendency to recur.
| Characteristic | Benign | Malignant | Borderline |
|---|---|---|---|
| Cell structure | Mature, differentiated | Undifferentiated or partially mature | Mature, differentiated |
| Growth pattern | Slow, expansive (with a capsule) | Rapid, infiltrating and invasive | Invasive |
| Recurrences and metastases | Do not recur, do not metastasize | Recur and metastasize | Capable of recurring |
Benign tumors grow "within themselves" (expansive growth). They do not destroy neighboring structures, but merely gently push them aside, forming a distinct connective tissue capsule at the border with healthy tissue.
Malignant tumors grow aggressively. They are characterized by infiltrative growth (destructive invasion into surrounding tissues) and invasive growth (invasion into blood and lymphatic vessels). Secondary changes frequently occur within their tissue: areas of necrosis, massive hemorrhages, myxoid change, and petrification.
> Clinical significance: Although the prognosis for these diseases is becoming increasingly optimistic, malignant tumors remain the second leading cause of death in developed countries (after cardiovascular pathology).
Nomenclature principles
Medical nomenclature of neoplasms is built on a strict principle: the suffix "-oma" is added to the root of the tissue of origin name.
Classification by histogenesis (tissue origin) includes the following basic terms:
- Benign formations originating from epithelial tissue are called epitheliomas.
- Malignant formations originating from epithelium are named carcinoma (carcinoma) or cancer.
- Malignant formations of mesenchymal origin are called sarcomas (sarcoma).
Important terminological distinction: In English-language medical literature, the word cancer denotes absolutely any malignant tumors, regardless of the tissue from which they originated. However, in professional Russian-language literature, the term "rak" (cancer) is applied exclusively to malignant tumors originating from the epithelium.
Briefly: answers to topical questions
What types of atypia are characteristic of malignant tumors?
Malignant tumors are characterized by both variants of morphological atypia: cellular and tissue.
- Morphological atypia — disruption of tissue and cellular structure. Tissue atypia includes disruption of the parenchymal-stromal ratio; cellular atypia is characterized by significant polymorphism of cells and nuclei.
- Biochemical atypia — alteration of the tumor cell metabolism, including the predominance of anaerobic glycolysis.
- Antigenic atypia — appearance of new antigens or loss of tissue-specific antigens.
- Functional atypia — loss of specialized functions of the progenitor cell or the appearance of an uncharacteristic function.
What are the main pathways of malignant tumor metastasis?
There are four main mechanisms of tumor cell dissemination from the primary site to other organs and tissues.
- Lymphogenic route — spread via lymphatic vessels (retrograde metastasis against the lymphatic flow is possible).
- Hematogenous route — dissemination via blood vessels.
- Perineural route — spread along nerve trunks.
- Implantation route — contact spread along serous membranes (leads to peritoneal carcinomatosis).
How are tumors classified by histogenesis?
By histogenesis, tumors are classified based on the type of tissue or cell from which they developed and whose differentiation features they have retained.
The following main groups are distinguished:
- Epithelial tumors: benign — epithelioma; malignant — cancer or carcinoma.
- Melanin-producing tumors.
- Neuroectodermal tumors.
- Meningovascular tumors.
- Tumors of the hematopoietic and lymphoid tissue.
- Mesenchymal tumors, including sarcomas — malignant tumors of mesenchymal origin.
What stages does tumor morphogenesis include?
Tumor morphogenesis includes sequential stages of neoplasm development, which in modern classification are divided into four stages.
- Pre-tumor stage — includes cellular hyperplasia and pre-tumor dysplasia.
- Stage of non-invasive tumor — formation of in situ carcinoma (intraepithelial carcinoma), in which the tumor does not invade surrounding tissues and lacks its own blood vessels.
- Stage of invasive tumor growth — invasion into surrounding structures.
- Metastasis stage — spread of cells from the primary focus.
Historically (according to L.M. Shabad), focal and diffuse hyperplasia, benign and malignant tumors were distinguished.
What systemic effects does a malignant tumor exert on the body?
A malignant tumor exerts a pronounced general effect on the body, manifested by the development of nonspecific systemic reactions and syndromes.
The main systemic influences include:
- Cancer cachexia — severe wasting of the patient with the development of brown atrophy of the myocardium, liver, and skeletal muscles.
- Cancer intoxication and anemia.
- Paraneoplastic syndromes — a complex of pathological processes affecting regulatory systems, metabolism, and immunity (e.g., Trousseau syndrome — phlebothrombosis in cancer).
- Immunopathological processes.
How not to confuse the terms "carcinoma" (cancer) and "sarcoma"? Remember: Sarcoma is a malignant tumor arising from connective (mesenchymal) tissue. In Russian medical terminology, the word "rak" (cancer) is strictly reserved for malignant tumors of epithelial origin.
Class and exam questions
Why doesn't tumor cell death stop neoplasm growth?
Due to apoptosis pathology. It is incomplete in nature, and mitogenic factors are released from disintegrating apoptotic bodies. They paradoxically stimulate the proliferation of neighboring tumor cells.
How does expansive growth differ from infiltrative growth?
With expansive growth, a tumor grows "within itself," slowly pushing aside healthy tissue and forming a capsule around itself. Infiltrating growth is the aggressive and rapid invasion of neoplasm elements directly into surrounding tissues, destroying them.
Can a tumor composed of mature cells behave aggressively?
Yes, this behavior is characteristic of borderline tumors. They consist of differentiated (mature) cells, which is typical of benign processes, but they are capable of invasive growth and recurrence.
What else to study on this topic
- Mechanisms of somatic and germline mutations in neoplasms
- Pathological mitotic figures and cell cycle disruptions
- Secondary changes in malignant tumors (necrosis, hemorrhage, mucinous degeneration, petrification)
- The role of the stroma in the autonomous regulation of tumor growth
- Stages of connective tissue capsule formation in expansive growth
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