What are the basic knowledge about rectal cancer

Rectal carcinoid is a common type of digestive tract carcinoid. In the past, the incidence of rectal carcinoid was second only to the appendix and jejunum, but recent reports show that rectal carcinoid ranks first among gastrointestinal carcinoids. Despite this, rectal carcinoid is still relatively rare.

1. Clinical characteristics

Rectal carcinoid is a potential malignant tumor that grows slowly, has a long course of disease, and rarely metastasizes. 1/2 to 2/3 of patients are asymptomatic when diagnosed, and most are accidentally discovered during examinations of other intestinal lesions. A small number of patients may have symptoms such as discomfort in the anus and rectum, constipation, changes in bowel habits, and blood in the stool. Anal examination often touches round, smooth, movable, and hard nodules. It is often found during endoscopic examination. Most rectal carcinoids do not show symptoms of "carcinoid syndrome" such as facial flushing and diarrhea, which may be because rectal carcinoids rarely secrete large amounts of 5-hydroxytryptamine. The peak age of onset of rectal carcinoid is 41 to 70 years old, with an average of 52 years old. The incidence of men and women was previously believed to be equal, but recent reports have shown that it is more common in men (the male-to-female ratio is 1.7:1).

2. Diagnosis

Since most rectal carcinoids lack specificity or have no obvious symptoms at all, their diagnosis is mainly based on rectal digital examination, endoscopy and X-ray examination. The diagnosis must be based on pathological examination. In addition to HE staining, suspicious lesions should be subjected to silver staining, immunohistochemistry and even immunoelectron microscopy for biopsy specimens. Since rectal carcinoids mostly occur in the 4-13 cm intestinal segment above the dentate line, and most of them are located below 8 cm, and are more common on the anterior wall, they can often be touched by rectal digital examination. If a round, smooth submucosal nodule is found, be alert to this disease. Endoscopy and biopsy are the main methods for diagnosis. The typical endoscopic manifestation is a submucosal nodular protrusion, which is mostly less than 1 cm in diameter, hard, and often movable by pushing. The surface mucosa is smooth and the color is pale and yellowish.

Treatment

Rectal carcinoid has a low potential for malignancy. If its diameter is <2cm, it is mostly benign, and if it is >2cm, it is mostly malignant. The principle of treatment for this disease is to determine the resection method based on the size of the tumor, combined with the depth of infiltration and histological type. If the tumor is ≤1.0cm, there is no infiltration beyond the submucosal layer, and there are no atypical histological manifestations, endoscopic local resection can be performed. If the tumor is >2cm or invades the muscle layer, it should be radically resected as a malignant tumor. If the diameter is 1-2cm and does not invade the muscle layer, local extended resection can be performed through the sacrum or anus, and the resection range should include normal tissue 1cm away from the edge of the tumor. If liver metastasis occurs, hepatic artery catheterization and embolization, interventional chemotherapy, etc. should be performed at the same time as the primary lesion is removed. Metastatic lesions can also be removed when conditions permit.