Yes, there was somewhere a woman in 1000s U/ml and more reading and it was due to severe pelvic inflammation.
I copy from pub med:
"CA-125 is of little value as a screening test for ovarian carcinoma.
A brief list of the most common benign conditions associated with CA-125 increase includes
menstruation,
pregnancy,
benign pelvic tumors,
pelvic inflammatory diseases,
ovarian hyperstimulation syndrome,
peritonitis,
and many diseases leading to pleural effusion or ascites.
According to several studies, a marked increase in CA-125 of greater than 1000 units/mL, as seen in Case 2, and even up to 5000 units/mL, could be seen in some benign conditions.
This finding further limits the value of CA-125 as a potential noninvasive procedure to differentiate benign from malignant diseases.
Although values up to 10,000 units/mL are occasionally seen in patients with ovarian carcinoma, we are reluctant to state that any concentration of CA-125 can be clearly diagnostic of malignancy."
It is a screening marker to keep an eye on something, but it cannot say, where it came from.
'Cyst' is not 'cyst'. You know that cysts are normal, as long as ovaries are functioning, it depends if those cysts were functional. Cyst as liquid filled blob only is not the problem, it's when there is something in it.
Some cysts are endometriomas, hence fill with blood again and again. Yet this is not cancerous, but not normal.
(I had a teratoma, a benign tumor in a persisting cyst, 9cm. No one ordered CA125, we just took it out)
From CA 125 alone you can never say to have ovarian cancer, but one might like to take a persisting cyst out and work it up histologically, as this is the only way to have a definite diagnosis.
As I always also like to say, you rather want to know and deal with it.
You want to be on time and beat whatever it is.
So actually good, to be on the 'monitoring' train now in order to act in time in case something was up.
But as said, this is no way of a definite diagnosis.
She will probably need a lap and take anything suspicious out to get more information. Or maybe, if imaging looked too innocent of cyst, the test will be redone.
Yes, CA125 is highly unspecific and not an ovarian cancer marker only at all, but as well.
Best of luck for the best outcome as it must be very stressful for your mum!