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

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 1. ORGAN. ORGAN SYSTEM. ORGANISM

TUMORS

GENERAL CHARACTERISTICS OF TUMORS

2. FEATURES OF TUMOR GROWTH

Tumor growth is characterized by diversity. In general, a tumor always grows through the proliferation of its own Cells.

Tumors can grow without destroying surrounding Tissues by pushing them aside; this leads to stromal collapse and compaction of the surrounding tissues, resembling a capsule (pseudocapsule). This type of growth is called expansive. It is characteristic of most benign tumors and defines their benign nature.

In other cases, a tumor invades the surrounding tissues. This type of growth is called infiltrative and is characteristic of most malignant tumors, defining their malignancy. Due to infiltrative growth, malignant tumors are often fused with surrounding tissues (and thus immobile); their boundaries are difficult to determine during surgery, and even after surgery, recurrence is possible—The Development of a tumor at the site of the removed one.

The growth rate of tumors is determined mainly by their degree of maturity. An exception to this rule is certain types of tumors with a very slow growth rate (more than 10–12 years), notably Choriocarcinoma.

Tumors can exhibit exophytic and endophytic growth patterns. With exophytic growth, the tumor grows primarily into the lumen of a hollow organ, whereas with endophytic growth, it primarily invades its wall.

Tumors can be benign or malignant in terms of their Morphology and clinical course (Table 1.1).

Class="center">Table 1.1. Comparative characteristics of benign and malignant tumors

Benign tumors are characterized by: tissue atypia, slow expansive growth, absence of metastases, and lack of a general negative impact on the Organism. However, in certain locations, benign tumors can also have a clinically unfavorable course. For instance, a benign meningeal tumor, as it increases in volume, compresses the Brain, causing severe neurological disorders. Benign tumors can acquire malignant features, i.e., undergo malignant transformation.

Malignant tumors are accompanied by cellular and tissue atypia, infiltrative (invasive) growth, metastasis and recurrence, as well as a pronounced NEGATIVE IMPACT OF the tumor on the organism as a whole.

Metastasis (from Greek meta — transposition, change, and stasis — standing, station) is the primary pathway for the spread of Cancer cells from the primary site and the most characteristic feature of malignant tumors (carcinomas, sarcomas). As a result of metastasis, new foci of tumor growth are formed.

Metastases arise due to the dissemination of tumor cells via Blood flow (hematogenous metastases), Lymph (lymphogenous metastases), along perineural spaces (perineural metastases), or across serous or mucosal membranes in contact with the tumor node (contact metastases). Metastasis involves two sequential phenomena: cellular embolization and the implantation of cells at the site where they halt. Therefore, a tumor metastasis is an autotransplant, driven by the course of tumor development, its biological features, and the Specific characteristics of the tissue at the metastatic site.

Metastases can be intra-organ, regional, or distant.