How can you tell the difference in anal cancer and hemorrhoids?

Completely different: They are completely different. Hemorrhoids is just an engorgement of veins. The other is a solid mass. They look different-, they feel different. Cancer would look like an irregular looking, friable mass, firm/hard on palpation. While hemmorhoids-feel smooth, soft, vascular feeling- you know that it is blood vessel. Go to see your doctor and have it checked.

Probably biopsy.: These lesions can have very similar clinical presentation, with bleeding and a mass. Biopsy of the affected area would allow examination under a microscope to see if tumor is there. More extensive surgery may have to be done in both cases. Radiation and chemotherapy may be an option for anal cancer. Physical exam of the affected area by a doctor may be helpful.

Not always easy at: First, but unless the hemorrhoid is thrombosed, it usually reduces and eases with sitz/tub soaks, preparation h. Both are painful, the anal canal is inside the opening, and the rectum above. Both can be quite painful, external, and bleed. An expert needs to decide when to look higher and biopsy. Also, nodes in groin. Get a surgeon to help.