My husband has a large lump on his rear end close to his rectum. It is very sore to sit on, and yellowish-greenish thick pus comes out of it. I am not sure what it is, and he is not one to go to the doctor. Could it be a large pimple that is infected? Or something serious like cancer? It's been there about five months.

L.B.

I believe your husband has an infected cyst. A cyst is a sac of fluid, lined with a membrane, that develops abnormally within the skin or an internal organ. There are several types of cysts that occur in the perianal region (the area near the anus). Pilonidal cysts, common in young men, are thought to be due to a congenital abnormality. They form above the anus, usually in or just above the buttock crease. These cysts may not cause any symptoms and may be found only on a routine physical examination. Pilonidal cysts can rupture, resulting in a chronically draining opening in the skin. They are also prone to infection. When such a cyst becomes infected, it will cause pain and tenderness. An infected cyst, which is filled with pus, can rupture spontaneously, temporarily easing the symptoms. I believe this is what is occurring with your husband.

There are several other types of cysts that can cause similar symptoms. This would include the very common epidermal inclusion cyst, which occurs when skin tissue becomes trapped under normal skin, usually after a minor trauma. The trapped skin forms a cyst cavity filled with secreted oils and dead cells.

Another possible cause of your husband's illness is an anal abscess. This infection forms in the small glands of the anus. These abscesses are found in and around the anus itself. They are exquisitely painful, and the pus inside them is quite foul-smelling. However, I would not expect such an infection to last five months. From your question, I do not think this is what your husband has, but I could not tell for sure without examining him.

Regardless of the exact diagnosis, your husband needs to see a doctor. If it is any of the conditions I have mentioned, the treatment involves minor surgery. Without this intervention, he is likely to suffer for months or even years. I do not think that there is much likelihood that he has anything more serious, such as cancer, but even that cannot be excluded without a thorough evaluation. I think that if you reassure your husband that it is unlikely that he has anything really serious, and that he can be cured with a relatively simple procedure, he may be more willing to seek medical care.