MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 1. ORGAN. ORGAN SYSTEM. ORGANISM

TUMORS

GENERAL CHARACTERISTICS OF TUMORS

1. PROPERTIES OF TUMORS

During their growth, Cells acquire new properties that are not typical for them under normal conditions, such as autonomy, uncontrolled growth, anaplasia, or cataplasia.

Autonomy and uncontrolled growth refer to unresponsiveness to regulatory mechanisms that normally limit or accelerate Cell proliferation. Tumor growth ceases only with the death of the Organism. In tissue culture, growth is sustained indefinitely—unlike normal tissue—due to the absence of the "Hayflick limit" (each Cell Nucleus contains an Aging mechanism that limits the number of cell divisions, which is lost when cells undergo tumor transformation).

Anaplasia, or cataplasia, is the loss by tumor Cells of the ability—characteristic of differentiated (mature) normal cells—to form specific tissue structures and produce specific substances.

The cells and stroma of a tumor differ from the normal structures of the tissue from which the neoplasm originated. This divergence between the tumor and its tissue of origin is known as atypia. Morphologically, atypia can be tissue-based or cellular. Biochemical and antigenic atypia may also occur.

Tissue atypia is characterized by the disruption of normal tissue relationships specific to a given organ, specifically regarding The ratio of parenchyma to stroma and their spatial arrangement within the tumor.

Cellular atypia is characterized by alterations in parenchymal cells as they lose the capacity for maturation and differentiation. Occasionally, these cellular changes are so profound that identifying the parent tissue becomes difficult. When morphological cataplasia reaches its extreme degree, the tumor Structure becomes simpler and monomorphic, making anaplastic tumors from different Organs strikingly similar to one another. Cellular atypia is a hallmark of malignant tumors.

Biochemical atypia indicates the predominance of anaerobic processes over oxidative METABOLISM within the tumor. Elevated anaerobic activity leads to the accumulation of lactic acid, increasing the tumor's resemblance to embryonic tissue, which also relies predominantly on oxygen-independent metabolism. Under these conditions, cells become more sensitive to cytostatic drugs, radiotherapy, etc.

Antigenic atypia of a tumor manifests as a unique antigenic profile specific to each individual neoplasm. In undifferentiated malignant tumors, antigenic simplification occurs, whereby the variety of Antigens synthesized by The Cell is significantly reduced.