Intestinal cancer

Precancerous conditions and pathogenesis

The development of a malignant neoplasm in the colon rarely occurs on the background of a completely unchanged mucosa. Several key nosologies are distinguished that are considered precancerous states:

• Intestinal polyps: both solitary and multiple lesions.
• Inflammatory bowel disease (IBD): ulcerative colitis (UC) and Crohn's disease.

The morphological substrate for cancer formation is epithelial dysplasia or neoplasia (adenoma). It is important to note that areas of dysplastic changes can occur even in hyperplastic polyps. Although such polyps are not strictly considered tumors by themselves, they possess proven malignant potential.

The risk of developing oncology in IBD varies. In ulcerative colitis, the incidence of colon cancer significantly exceeds similar rates in the general population. Crohn's disease is also associated with a high risk of malignancy, although this risk is statistically lower than in patients with UC.

Synchronous polyps: surgical tactics

In clinical practice, when diagnosing rectal cancer, physicians face a high probability of detecting so-called synchronous lesions — additional polyps or even areas of cancer in more proximal segments of the large intestine.

The optimal management strategy for such patients implies that, if technically feasible, it is preferable to remove synchronous polyps prior to initiating primary cancer treatment. This decision has strict clinical justification:

1. Elimination of malignant transformation risk: during antitumor treatment (which takes time), polyps can increase in size or undergo malignant transformation. Early removal neutralizes this threat.
2. Prevention of non-compliance: reduces health risks for the patient in case they subsequently fail to follow medical recommendations or refuse further endoscopic examinations.

Clinical and morphological manifestations

General principles of oncological semiotics are also applicable to colorectal cancer. The disease is characterized by two fundamental clinical phenomena:

• Tumor phenomenon: visually or radiologically determined presence of "tissue excess" (the neoplasm itself or an ulcerative defect).
• Destruction phenomenon: breakdown of tumor tissue, which clinically often manifests as bleeding.

Dependence of symptoms on tumor localization: The clinical presentation of colorectal cancer is extremely variable and directly depends on the anatomical location of the lesion. This is due to the physiological and anatomical features of different parts of the bowel.

• Right hemicolon: characterized by a wide lumen and liquid contents. Because of this, tumors here rarely cause obstruction. The clinical picture is dominated by symptoms of chronic blood loss, the development of anemia, pronounced general intoxication, and a palpable abdominal mass.
• Left hemicolon: has a narrower lumen, and fecal masses here are dense. Tumors in this location more often lead to symptoms of bowel obstruction. Patients complain of persistent constipation, which may alternate with diarrhea, abdominal distension, and cramping pain.
• Rectum: cancer of this localization is most typically characterized by the appearance of blood and mucus impurities in the stool, painful false urges to defecate (tenesmus), and a constant feeling of incomplete bowel emptying.

Class and exam questions

What else to study on this topic

• Macroscopic growth patterns of colorectal cancer
• Histological classification of adenocarcinomas
• Metastatic pathways of colorectal cancer
• Complications of colon cancer
• Causes of death in colorectal cancer

Other topics in the "Additional Topics" section

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