It is, of course, impossible for me to make a diagnosis, or any specific treatment recommendations, over the Internet. Generally speaking, young women frequently develop benign cysts of the ovary due to normal ovarian function. Rarely (and very rarely in your age range), malignant cystic lesions of the ovary can develop. There are certain findings on ultrasound (and CT scans) that are more suggestive of potentially malignant lesions. These include cystic lesions that are enlarging over time (on serial exams), complex cystic lesions, cystic lesions with certain patterns of calcification in them, and cystic lesions that have increased blood flow on the Doppler studies that are performed during ultrasound, for example. When suspicious findings are encountered, a blood test for a substance that is sometimes elevated in cases of ovarian cancer (CA 125) may be ordered, although a normal CA 125 level in the blood does not rule-out ovarian cancer. Also, a family history of ovarian cancer or/and early-onset breast cancer can increase a young woman's risk of having either (or both) of these types of cancer.
It is very unlikely that your back pain is being caused by a single 1/2 inch cyst on your ovary.
The likelihood that the ultrasound findings that you have described are due to an ovarian cancer are small. However, as I have already mentioned, it is absolutely impossible for me to render specific diagnoses or specific treatment recommendations for patients that I have not personally evaluated before. Therefore, my recommendation is that you visit your gynecologist again, and communicate your ongoing anxiety and concerns regarding this cystic lesion in your ovary. At a minimum, I would suggest repeating the pelvic ultrasound again, 3 to 6 months after the previous study. Also, if the radiologist who reviewed your last ultrasound has any concerns that this cystic lesion might be suspicious, then a CA 125 level and, possibly, a CT scan might be in order. If any of these additional studies are suspicious, then a laparoscopy can be performed by your gynecologist to further evaluate this cyst, and possibly biopsy or remove this ovarian lesion, if appropriate.
Robert A. Wascher