Tumor classification

Basic classification principles

In surgical and oncological practice, all detected neoplasms are strictly systematized based on three fundamental diagnostic criteria.

1. First, physicians always consider the original tissue type from which the pathological focus originated. This criterion is called histogenesis. Several broad groups are distinguished: epithelial, connective tissue, muscle, vascular, and neural neoplasms. In addition, mixed variants are frequently encountered.
2. Second, precise localization of the process, i.e., the specific affected organ of the patient, is of utmost importance. This can be lung tissue, the stomach wall, skin, bone structures, and many other areas.
3. Third, specialists perform a detailed analysis of the morphological features of the tumor and the nature of its clinical course, which makes it possible to reliably assess the ability of the altered cells to further spread throughout the body.

Benign neoplasms

Benign processes are characterized by a relatively favorable and predictable clinical course. One of the main distinguishing features is the mandatory presence of a distinct capsule. This capsule reliably isolates the pathological focus from surrounding healthy tissues. Such neoplasms grow relatively slowly, demonstrating the so-called expansive growth pattern. With this developmental variant, healthy tissue is not destroyed, but is merely gently pushed aside as the tumor volume increases. It is important to note that the cells retain a high degree of differentiation—their histological structure differs minimally from the original parent tissue.

Such tumors never metastasize, do not invade neighboring anatomical structures at all (i.e., invasion is completely absent), and do not recur if the operating surgeon has performed their radical removal.

However, it is a mistake to assume they are completely safe. They can pose a direct, life-threatening danger if their increasing size causes physical compression of vital structures. Such critical zones primarily include:

• Meninges.
• Major nerve trunks and main blood vessels.
• Airways (including bronchi and trachea).
• Ureters and bile ducts.

In medical nomenclature, the names of benign tumors are traditionally formed based on the type of origin tissue. Thus, adenomas develop from glandular epithelium, myomas form from muscle fibers, lipomas from adipose tissue, chondromas from cartilaginous elements, neurinomas from neural structures, fibromas from connective tissue fibers, and specific congenital tumors formed from the rudiments of various organs are called teratomas.

Malignant neoplasms

In sharp contrast to their benign counterparts, malignant neoplasms completely lack a capsule. They are characterized by an extremely aggressive, rapid, and infiltrative growth pattern. This means that the pathological masses do not merely push aside, but irreversibly destroy and deeply invade adjacent tissues and organs.

Another critical feature is a pronounced metastatic potential—the process by which tumor cells detach from the primary focus and spread throughout the body via the bloodstream through blood vessels or via lymph flow through lymphatic vessels. Even after extensive surgical intervention, there remains a consistently high risk of recurrence—the regrowth of the neoplasm at the exact same site.

Malignant processes exert a destructive systemic effect on the entire human body. The patient gradually develops a severe condition known as cancer cachexia (or cancer intoxication). Clinically, it manifests as pronounced weight loss, progressive anemia, and extreme general exhaustion, referred to in medicine as cachexia.

Based on their histogenetic origin, this aggressive group is typically divided into two main types:

• Carcinoma (cancer)—pathology that develops exclusively from epithelial tissue. This is the most common variant in clinical practice, accounting for the vast majority—about 95%—of all diagnosed malignancies.
• Sarcoma (sarcoma)—a neoplasm originating from connective tissue structures. It is significantly less common, accounting for about 5% of total cases. This category traditionally includes severe pathologies such as osteosarcoma, lymphosarcoma, myosarcoma, and angiosarcoma.

Class and exam questions

What else to study on this topic

• Mechanisms of cell metastasis via lymphatic and blood vessels.
• Pathogenesis of cancer intoxication and systemic cachexia.
• Differences between cells with high and low degrees of differentiation.
• Features of the formation and clinical course of congenital teratomas.

Other topics in "CHAPTER 14. TUMORS"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.