Cecal cancer is a malignant tumor arising from the cells of the cecal wall—the initial segment of the large intestine located in the lower right abdomen at the junction of the ileum and the colon. It may invade deeper layers, extend into adjacent tissues, or spread to distant sites through the bloodstream or lymphatic system. This cancer accounts for approximately 10–15% of colorectal cancers, occurs more commonly in older adults, and is often diagnosed through iron-deficiency anemia or occult gastrointestinal bleeding. Colorectal cancer has more than 1.9 million new cases annually worldwide; in Iran, it represents about 9–10% of all cancers and is among the most common malignancies. The proportion of cecal cancers generally aligns with global patterns.
Ascending colon cancer is a malignant proliferation of cells in the ascending segment of the colon, located after the cecum in the lower right abdomen and extending upward. The cancer typically originates in the colonic mucosa and may invade deeper layers, spread to nearby lymph nodes, or metastasize to distant organs such as the liver and lungs via the bloodstream. This subtype accounts for approximately 20% of all colorectal cancers, often remains asymptomatic for a long period, and is frequently diagnosed at more advanced stages. Globally, its incidence is increasing with aging populations and Westernized lifestyles. In Iran, cancer registry data similarly show a rising trend—especially in urban regions—likely associated with dietary changes and physical inactivity.
Transverse colon cancer is a malignant growth of cells in the horizontal, mid-section of the large intestine, which extends across the upper abdomen from right to left. This cancer typically originates in the colonic mucosa and may invade deeper layers, spread to regional lymph nodes, or metastasize to distant organs. It accounts for roughly 10% of colorectal cancers and is less common than right-sided or sigmoid colon cancers. However, because its symptoms are often nonspecific—such as diffuse abdominal pain or subtle changes in bowel habits—it is frequently diagnosed at a later stage. Globally, its proportion has remained relatively stable, while in recent years a modest increase has been reported in Iran, though it still remains less common than cancers in other colonic segments.
Descending colon cancer is a tumor that arises from the inner lining of the large intestine in the descending segment (on the left side of the body). It may initially grow without pain or noticeable symptoms, then progressively invade deeper layers of the bowel wall, spread to nearby lymph nodes, or metastasize through the bloodstream to other organs such as the liver or lungs. As the tumor enlarges, patients may experience changes in bowel habits, left-sided abdominal discomfort, or the passage of blood in the stool. Because the descending colon has a narrower lumen compared to the right colon, these tumors may present earlier with obstructive symptoms. Early detection through screening colonoscopy greatly improves treatment outcomes and long-term survival.
Sigmoid colon cancer is a malignant tumor that arises from the mucosa of the sigmoid segment of the large intestine (near the rectum). It may invade deeper layers, spread to regional lymph nodes, and metastasize to organs such as the liver or lungs through the bloodstream or lymphatic system. This cancer accounts for approximately 25–30% of colorectal malignancies, and because of its proximity to the rectum, it is often detected earlier due to symptoms such as bleeding, altered bowel habits, or a feeling of incomplete evacuation. Globally and in Iran, it is one of the most common sites of colorectal involvement, and in Iran the average age of patients has been reported to be lower than in Western countries.
The rectum is the final portion of the large intestine, located approximately 10 to 15 centimeters before the anus. Rectal cancer refers to the malignant growth of cells in this region, and because of its location within the pelvis and its proximity to nerves, the bladder, and reproductive organs, its treatment is more complex and often managed with a combination of surgery, chemotherapy, and radiation therapy. This cancer accounts for about 30–35% of colorectal cases; its incidence has declined in Western countries due to screening programs, but has been increasing in developing countries, including Iran. In Iran, its proportion is similar to global figures, but the age of onset is lower, with a significant number of patients being under 50 years old.
Anal cancer is a malignant growth of cells in the anal canal or the surrounding perianal region, with the most common type being squamous cell carcinoma, which arises from the surface epithelial cells of the anus. The disease typically presents with a mass, a persistent ulcer, or bleeding, and is most often treated with a combination of radiation therapy and chemotherapy. Its risk is increased in individuals with persistent infection by high-risk HPV types, men who have sex with men, people with HIV or immunosuppression, and those with multiple sexual partners. This cancer accounts for less than 2% of lower gastrointestinal malignancies, and its global incidence is rising; in Iran, reported cases are fewer, but the prevalence may increase with rising HPV rates.
