Nature of Neoplasms and Epidemiology
Any neoplasm (Neoplasma) is a standard form of aberrant tissue growth. This complex pathological process always arises under the damaging influence of specific factors known in medicine as carcinogens. Their impact triggers uncontrolled pathological proliferation of tissue that the organism cannot halt on its own.
Epidemiological statistics clearly demonstrate the scale of the issue: incidence varies across countries but remains high, averaging 190 to 300 cases per 100,000 population. The case fatality rate averages around 20%. Globally, neoplasms firmly occupy second place among causes of death, trailing only cardiovascular diseases. Examining cancer mortality specifically, lung cancer is the absolute leader with a steadily rising incidence. It is followed by colorectal cancer, breast cancer, and prostate cancer in descending order of mortality.
Tumor Atypia as the Principal Marker
The key and most recognizable feature of any tumor is the presence of tumor atypia. This means that cells lose their normal properties and begin to behave abnormally. This phenomenon affects several crucial aspects of tissue homeostasis:
- Atypia of growth: cells completely escape organismal control and begin to proliferate autonomously.
- Atypia of metabolism: core metabolic processes within the affected structures undergo fundamental changes.
- Atypia of structure: normal histological architecture of the tissue is disrupted.
- Atypia of function: the tissue either completely ceases to perform its specific physiological tasks or does so improperly.
Based on the structural features of tumor cells and tissues, as well as clinical behavior, neoplasms are fundamentally classified into two major groups.
Benign Neoplasms
This group of neoplasms is characterized by a relatively favorable clinical course. Typical examples include teratomas, myomas, and lipomas.
Their primary morphological feature is a close structural and internal resemblance to the normal, healthy tissues from which they originally arose. Cells retain a high degree of differentiation—their architecture closely corresponds to the tissue of origin. The critical clinical criterion distinguishing this group is that benign variants generally do not metastasize, meaning they do not spread their cells to other body systems.
Malignant Neoplasms
Unlike the previous group, these tumors (which include teratoblastomas, carcinomas, and sarcomas) differ substantially from the original normal tissues. Definitive diagnosis and malignancy status are established exclusively through a comprehensive set of morphological, clinical, and prognostic criteria.
Key characteristics of malignant cells and tissues:
- They are poorly differentiated, meaning they have almost completely lost their initial specialization.
- They form completely anomalous, atypical tissue structures.
- They exhibit a capacity for extremely rapid volume and mass expansion.
- They demonstrate invasive growth — aggressively invading and destroying surrounding normal tissues along their path.
- They are prone to metastasis — a process where cells migrate beyond the primary growth zone. Detached elements form distant secondary foci (metastases) that always retain the same histological structure as the primary tumor.
Classification by Cellular Origin
Depending on which normal cell type undergoes pathological transformation, pathophysiology classifies malignant tumors into several specific categories:
- Carcinomas (true cancer) — malignant tumors formed exclusively from mutated epithelial cells.
- Adenocarcinomas — specific malignant neoplasms developing from secretory epithelium (glandular structures).
- Sarcomas — malignant tumors originating from various connective tissue elements. This broad group includes neoplasms arising from blood cells, as well as bone, cartilage, and other connective tissue structures.