Malignant origin of the stromal component of Wilms' tumor.

or quarterly cyclic hormone therapy (2 mg of estradiol on days 1-78 and 1 mg of estradiol on days 79-84, with 1 mg of norethindrone on days 69-78) was stopped after 2-3 years of the planned 5 years of treatment because of an unacceptably high rate of endometrial pathology (including one en-dometrial cancer) in the quarterly compared with the monthly cycle group (6.2% versus 0.8%; P ‫ס‬ .004). Although this study used different hormones than those in the U.S. trial, it raises questions about the safety of quarterly cyclic therapy. Current hormone replacement regimens might be safe, but are they optimal? For short-term treatment of menopausal symptoms , MPA appears safe and effective. However, growing evidence suggests that micronized progesterone might be a better progestin for long-term use. Neither MPA nor progesterone added to estrogen alters the beneficial effect of estrogen in preventing loss of bone density (8), but evidence suggests that MPA negates more of the beneficial effects of estrogen on the cardio-vascular system than micronized progesterone. MPA reduces the high-density lipoprotein-increasing effect of unopposed estrogen more than micronized progesterone does (9) and may reduce the beneficial effect on atherosclerosis (10) and on coronary vascu-lar tone (11,12). The PEPI Trial found no increased risk of endometrial hyperplasia in women who were randomly assigned to cyclic therapy with daily conjugated estrogens plus micron-ized progesterone given at a dose of 200 mg daily for 10 days per month, but no studies of the effect of micronized progesterone on endometrial cancer risk have been published. replacement therapy and endometrial cancer risk: a meta-analysis. Risk of endometrial cancer in relation to use of oestrogen combined with cyclic progestagen therapy in postmenopausal women. Lancet 1997;349:458-61. (5) Woodruff JD, Pickar JH. Incidence of endometrial hyperplasia in post-menopausal women taking conjugated estrogens (Premarin) with medroxy-progesterone acetate or conjugated estrogens alone. The Menopause Study Group. (9) Effects of estrogen or estrogen/progestin regimens on heart disease risk factors in postmenopausal women.progesterone acetate antagonizes inhibitory effects of conjugated equine estrogens on coronary artery atherosclerosis. Assessment of less than monthly progestin therapy in postmenopausal women given es-trogen replacement. In this issue of the Journal, Zhuang et al. (1) provide molecular evidence for an important proof of principle, mainly that the various histologic components of a tumor arise from a common clone. This principle has long been accepted in the leuke-mic stem cell disorder chronic myeloid leukemia, where the Philadelphia chromosome …