DEAR DR. DONOHUE: I have an abdominal aortic aneurysm. In January 2004, it was 3.9 centimeters. I had an ultrasound last week, and it was the same size. My doctor said he’ll check me again, but that if I don’t feel right, I should get to a hospital ASAP. Can you be more specific about this? – N.O.

ANSWER: An aneurysm is a bulge at a weak spot on an artery. It looks like a blister. If the aneurysm breaks, massive bleeding threatens life.

The aorta, the body’s largest artery, begins at the heart and travels down the chest and abdomen. At the lowermost part of the abdomen it divides into two arteries, one for each leg. The abdominal section of the aorta is the place where many aneurysms develop.

Most abdominal aortic aneurysms are discovered accidentally, because they don’t often produce symptoms. A doctor might feel one when examining the abdomen, or one might show up on an X-ray or ultrasound taken for another reason.

Treatment of aneurysms depends on their size. If an aneurysm is less than 5.5 cm (about 2 inches) in diameter, monitoring it with ultrasound examinations is the usual path chosen, because such aneurysms rarely break. Larger ones or ones that grow more than 1 cm (about half an inch) in one year are generally operated on.

“Not feeling right” means having abdominal or low-back pain, which is a symptom of an aneurysm that is leaking blood. This is an urgent matter. Life is lost unless immediate surgery is done.

The traditional repair of a large aneurysm is the insertion of a graft to reinforce the weakened artery wall. Now doctors can take care of some aneurysms by inserting a stent through a leg artery and inching it upward to the target area in the aorta. The procedure is quite similar to placing stents in heart arteries that have become obstructed with cholesterol buildup.

DEAR DR. DONOHUE: I have basal cell carcinoma. It has me worried. It’s a patch of skin about a half-inch in diameter on my forehead. I have to have it surgically removed. Can it come back? What causes it? What is a basal cell? – K.L.

ANSWER: The outermost level of skin, the epidermis, has five layers. Its lowest layer is composed of basal cells. It is from those cells that basal cell skin cancer arises.

This is the most common skin cancer. It usually appears after age 40, and most of the time it is found on the head or neck. Ultraviolet light plays a role in its development, so people with fair skin, blue eyes and red hair – the people most sensitive to sunlight – are the ones most apt to come down with basal cell cancer. Scars and healed burns and cuts also predispose people to it. For many, no reason is found.

A typical basal cell cancer starts out as a small, dome-shaped little nodule whose center forms a crater, and the crater eventually becomes a sore. The sore bleeds, and then a scab covers it. It can heal, but it comes back again and again. A nonhealing sore, therefore, is something a doctor should examine.

Basal cell cancer rarely spreads to distant places and almost never is a menace to life. Untreated, however, it can bore deeply into the skin and the tissues beneath the skin.

Surgical removal predictably effects a cure. There are other methods of dealing with it. Drying one with an electric current is an example of an alternate treatment.

Basal cell cancer does recur. Furthermore, having had one basal cell cancer puts a person at greater risk of having another. You and your doctor have to watch your skin carefully for the next five years, the time when most recurrences happen and when most second cancers arise.

DEAR DR. DONOHUE: My husband has used chewing tobacco for half of his life. He’s only 28. Can you provide a reason he should quit, aside from the fact that our 2-year-old son mimics his every move? – H.H.

ANSWER: The chances for a chewing-tobacco devotee to come down with cancer of the mouth or tongue are 50 times greater than the chances for a nonuser to do so. That’s only one of many reasons for him to quit.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.