Proximal is a word pathologists use to describe the first part of a large tissue sample. It can also be used to describe tissue closer to the middle or centre of the body. In pathology, a tissue sample is called a specimen.
For example, the colon is a long tube that starts at the end of the small bowel and ends at the anal canal. The colon is divided into six parts: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The cecum would be described as the proximal part of the colon because it is the first part of the colon. It is also closer to the centre of the body.
The opposite of proximal is distal. Distal is used to describe the last part of a large tissue sample. It can also be used to describe tissue farther from the middle or centre of the body. Based on the example above, the rectum would be considered the distal part of the colon.
The word proximal can be used even when only a part of an organ is removed. For example, if the sigmoid colon and rectum are surgically removed, the sigmoid colon would be described as the proximal part of the specimen and the rectum would be described as the distal part of the specimen.