Colorectal carcinoma - causes, symptoms, diagnosis, treatment, pathology

Summary

Colorectal carcinoma, commonly known as colon cancer, is a prevalent and often deadly disease affecting the large intestines, including the colon and rectum. It typically arises from adenocarcinomas, which originate from the intestinal gland cells. The disease can be caused by sporadic mutations or genetic factors like the APC gene. Symptoms vary based on tumor location but may include abdominal pain, weight loss, and bowel obstruction. Diagnosis often requires colonoscopy and fecal occult blood testing, with treatment options ranging from surgery to chemotherapy, depending on the cancer's stage.

Takeaways

• 🌐 Colorectal carcinoma, also known as colon cancer, is a malignant condition affecting the large intestine, including the colon and rectum.
• 📍 The large intestine is divided into intraperitoneal and retroperitoneal spaces, each housing different parts of the colon and rectum.
• 🏠 The gastrointestinal tract walls consist of four layers: serosa/adventitia, muscular layer, submucosa, and mucosa, which is in direct contact with digested food.
• 🔬 Most colorectal carcinomas are adenocarcinomas, originating from cells lining the intestinal glands or colonic crypts.
• 🧬 Colorectal tumors often result from sporadic mutations, but some are due to hereditary genetic mutations like the APC gene, which is a tumor suppressor.
• 🔄 The APC protein's normal function is to induce apoptosis in cells with excessive mutations; a mutated APC gene can lead to uncontrolled cell division and polyp formation.
• 🔎 Other genetic mutations, particularly in DNA repair genes, can also contribute to the development of polyps and eventually adenocarcinomas.
• 📊 Colorectal cancer is staged from 0 (carcinoma in situ) to IV (metastatic), with increasing severity and complexity of treatment.
• 🚨 Risk factors for colorectal cancer include non-modifiable factors like age and gender, and modifiable factors such as diet, smoking, and obesity.
• 🩺 Symptoms of colorectal cancer can vary based on the tumor's location and size, with right-sided tumors causing less obstruction and left-sided tumors leading to bowel obstruction.
• 🛠 Treatment options for colorectal cancer range from surgical resection for early-stage cancers to chemotherapy for metastatic disease, aiming to alleviate symptoms.

Q & A

What is colorectal carcinoma and where does it occur?

Colorectal carcinoma, also known as colon cancer, is a type of cancer where malignant or cancerous cells arise in the large intestines, which includes both the colon and rectum.

What are the two spaces in the abdominal cavity where the large intestine is found?

The two spaces in the abdominal cavity are the intraperitoneal space and the retroperitoneal space. The large intestine weaves between these spaces.

What are the layers of the gastrointestinal tract, starting from the outermost layer?

The layers of the gastrointestinal tract are: 1) Serosa (outermost layer in intraperitoneal parts) or Adventitia (in retroperitoneal parts), 2) Muscular layer, 3) Submucosa, and 4) Mucosa (innermost layer).

What type of cells do most colorectal carcinomas originate from?

Most colorectal carcinomas are adenocarcinomas, meaning they arise from the cells lining the intestinal glands.

How do genetic mutations like APC mutations contribute to colorectal cancer development?

The APC gene is a tumor suppressor that triggers apoptosis when cells accumulate mutations. A mutation in the APC gene allows mutated bowel cells to divide uncontrollably, potentially forming polyps, which may later evolve into malignant tumors.

What is the difference between adenomatous polyps and serrated polyps in terms of their genetic mutations?

Adenomatous polyps often have mutations in the APC gene, while serrated polyps typically involve defects in DNA repair genes. Serrated polyps have a sawtooth appearance under a microscope.

How is colorectal cancer categorized into stages?

Colorectal cancer is categorized into stages: Stage 0 (carcinoma in situ, no growth beyond mucosa), Stage 1 (tumor grows beyond mucosa but not to lymph nodes or distant organs), Stage 2 (invades whole colonic or rectal wall, possibly nearby organs), Stage 3 (spreads to lymph nodes), and Stage 4 (spreads to distant organs, like liver or lungs).

What are some modifiable and non-modifiable risk factors for colorectal cancer?

Non-modifiable risk factors include being an elderly male and having inflammatory bowel disease. Modifiable risk factors include smoking, eating a lot of red meat, low fiber intake, and obesity.

What are common symptoms of tumors in the ascending (right) colon compared to the descending (left) colon?

Tumors in the right colon usually cause vague abdominal pain and weight loss, and may lead to iron deficiency anemia due to bleeding. Tumors in the left colon often cause bowel obstruction, abdominal pain, and bloody stools due to their ring-shaped mass structure.

What diagnostic tools are used to detect colorectal cancer?

Diagnostic tools include colonoscopy, fecal occult blood tests, and barium enemas. During a colonoscopy, polyps are examined and biopsied. Fecal occult blood tests check for gastrointestinal bleeding, and a barium enema helps detect abnormalities through X-rays.