DEAR DR. DONOHUE: Our family would like to know the differences between lymphoma, Hodgkin’s disease and non-Hodgkin’s lymphoma. How do you get these? Which did Jackie O. have? Why wasn’t her condition diagnosed, and why wasn’t it put in remission? – J.S.

ANSWER: Lymphoma is cancer of the lymph nodes, sometimes with involvement of the spleen, liver and bone marrow. The two most common kinds of lymphoma are Hodgkin’s disease and non-Hodgkin’s lymphoma.

Annually, there are about 7,800 new cases of Hodgkin’s disease in the United States. The two peak ages when it develops are the 20s and the 60s, but that’s not to say it can’t happen at any time. The most prominent sign of Hodgkin’s disease is nontender lymph-node enlargement along with fever, night sweats and weight loss.

Evidence points to an association between the Epstein-Barr virus and Hodgkin’s disease, but the matter is not definitely proved.

When Hodgkin’s is discovered early and is localized to a few nodes, cure can be expected nine times out of 10 with chemotherapy and radiation.

Non-Hodgkin’s lymphoma is more common, with about 54,000 new cases yearly in the U.S. Its signs are similar to Hodgkin’s disease: painless lymph-node enlargement, fever and weight loss. Frequently, early detection and treatment can put it into remission, with only slightly less success than with Hodgkin’s disease. Reputed causes include exposure to some chemicals, treatment of some cancers and possibly a viral infection.

Both illnesses can kill. There are aggressive forms of these cancers that don’t respond well to treatment. Furthermore, there are four distinct varieties of non-Hodgkin’s lymphoma, each having a different prognosis.

I don’t know which kind of lymphoma Jackie O. had. It had to have been a very aggressive one.

DEAR DR. DONOHUE: If you have had bypass surgery, can you use a hot tub or whirlpool bath? – V.M.

ANSWER: Most bypass patients can get into a hot tub, a whirlpool or a sauna. Heat makes the heart beat faster to bring blood to the skin surface to keep the body cool, but this is not usually a great strain on the heart. A safe temperature for a hot tub or whirlpool is 104 F (40 C), and for a sauna, 140 F (60 C). You should limit your time in all three to 15 minutes.

All three could be a danger for some heart patients and for hypertensive patients on particular high-blood-pressure medicines. Therefore, your personal physician has to give you approval for using them.

The booklet on coronary artery disease presents the general picture of people who have had bypass surgery or who are candidates for it. Readers can obtain a copy by writing: Dr. Donohue – No. 101, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: A fellow worker has developed leukemia. He is only 17. My mom says that bone-marrow transplants for leukemia patients only add seven years to their lives, but that was some time ago, when she worked in a hospital. Is there any hope for my friend, or will he die young? – S.C.

ANSWER: Leukemia is cancer of white blood cells, and there are many kinds, each behaving differently and each having a different prognosis. However, the outlook for leukemia patients has greatly changed since your mother was working in a hospital. Many leukemias – once thought of as incurable – are now being put into remission, and cure is possible for some.

Chemotherapy has greatly changed the odds of surviving leukemia. Sometimes it is combined with bone-marrow transplants or blood-derived stem-cell transplants.

There are some forms of leukemia that are lethal, but the majority of patients face a much brighter outlook than patients of decades past had.

There is much hope for your co-worker.

DEAR DR. DONOHUE: Years ago, after a biopsy of my testicle, I was diagnosed as having testicular atrophy. I was never told what this meant for me in terms of the future. I am 86 years old. I look forward to your thoughts on this condition for me. – M.S.

ANSWER: “Atrophy” means a wasting away of an organ. At 86, testicular atrophy has little impact on your health.

At a younger age, it could result in infertility or a deficient production of testosterone, the male hormone that keeps muscles and bones strong. It also could lead to erectile dysfunction.

DEAR DR. DONOHUE: I am approaching middle age, and I have a fibroid. It does not cause me any severe problem. I do have some lower back pain when I sit. When would you suggest getting it removed? – S.V.

ANSWER: If the fibroid is not causing a major problem in your life, I would not get it removed.

I would, however, check out the possibility that your lower back pain is not due to the fibroid.