There are indeed a number of different kinds of cancer in the anal region. You have asked several different questions just now regarding anal, rectal, and prostate cancer
. These are all different regions of the body and there are different subsets of anal cancer itself.
The anus is a circular muscle that functions as the gateway between the intestinal tract and the outside (usually the toilet). Because it is at the border between the skin and the type of tissue that lines the intestinal tract, you can have anal cancers that are squamous in origin (from the skin), basaloid transitional (from the transitional lining), or adenocarcinoma (from the intestinal lining), in addition to the rarer anal melanoma. Squamous is the most common (approximately 80%), most often due to the HPV virus.
Rectal cancer is typically of the adenocarcinoma variety. The rectum is the end of the intestinal tract, which is larger in diameter than the preceding segments and acts as a vault to store stool until it is time to defecate.
The prostate gland has nothing to do with the intestinal tract and instead is involved in reproduction. It is a gland which opens into the male urethra and secretes fluid which gives semen its thicker consistency. Prostate cancer is the most common cancer to develop in males, usually in the elderly. This is why it is recommended that elderly males have yearly prostate exams. Because the prostate is in the pelvis, it can actually be felt through the wall of the rectum, this is why your doctor
will perform a rectal exam with his finger when checking the prostate. This is why some people believe the prostate to be part of the intestinal tract, however, it is not, the rectal exam is simply the easiest way to examine it.
I do not know why your husband believes he has prostate cancer. Concerning signs would be unexplained weight loss, night sweats, fatigue, and change in urinary habits such as an increased difficulty urinating, or feeling an urgency to urinate but not being able to when getting to the toilet. However, the urinary problems are also common in benign prostatic hypertrophy which is far more common than outright cancer. If you and your husband are concerned regarding the possibility of prostate cancer you should talk to you primary care physician
for a prostate exam and PSA blood test, which is a marker that is sometimes helpful in detecting and/or monitoring prostate cancer.