Recent technological advances have allowed the evaluation of a large number of chemicals as potential tumour markers. In gynaecology there are three tumour markers of proven value Ca125, HCG and alpha-fetoprotein.
Ca125 is a tumour marker that is associated with ovarian cancer. Some ovarian cancers may not result in an increase in Ca125 levels. There are several reasons that limit the value of currently available tumour markers. Most tumour-associated markers are also produced by healthy tissues so that there is an overlap of levels between those with a tumour and healthy people. Ca125, the ovarian cancer marker, increases in 20% of healthy women during their periods and in 50% of women during pregnancy. It is non-specific and may be increased in some endometrial or bowel cancers. Raised levels may also be found in association with benign conditions of the ovary, pelvic inflammation and endometriosis.
The pre-placental tissue of pregnancy (trophoblast) produces human chorionic gonadotrophic hormone (HCG) and its presence is the first evidence of pregnancy. Occasionally (about one pregnancy in a thousand) in the UK, the trophoblast becomes an innocent tumour (hydatidiform mole). Rarely, this may become malignant choriocarcinoma; HCG levels are useful to monitor patients who have had a hydatidiform mole. Disgerminomas, (rare ovarian tumours in young women) may result in high levels of HCG. Alpha-fetoprotein (AFP) is produced by foetal tissues. When there is an open spina bifida the levels of AFP in the amniotic fluid and mother's blood rise. This was the first useful test for detecting spina bifida during pregnancy but has become superseded by ultrasound examination of the fetus. AFP levels may be increased in association with some rare
germ cell tumours of the ovaries.
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