Don't worry at this point at all.
First of all, your CA125 doesn't indicate anything. Is completely negative.
Having said though, a CA125 single value is never conclusive on its own.
It can be elevated (>35 or 41 U/ml, depends on test brand) also in benign situations like endometriosis or fibroids or simply be an individual healthy person with higher CA125 naturally, but can also be negative in ovarian cancer.
It is just one puzzle piece and at the moment, negative and good.
It usually is a value, that is monitored if it increased significantly over time when retested, if retesting was indicated in the first place. (depends on histological outcome)
Looked at your ultrasound (love it! Thank you!).
Nobody will be able to see,
if this was a
haemorrhagic cyst (with just an old blod clot),
endometrioma (which is also blod clots),
corpus luteum with solid structure (as it also happens to form)
dermoid
or boarderline tumor
or even malignant growth
like endometrioid carcinoma
especially because we have no further info
(wall thickness, ovarian tissue around, that looked normal. If yes, very likely benign. Doppler mapping ultrasound result.)
and also, because it is impossible to 100% diagnose what the solid is made of since so many different structures look the same in ultrasound.
It's an 'adnexal mass', it does need to be taken out....simply to know what it is.
A little story:
I had a 9cm cysts, gyn thought it to be a simple cyst (only black = liquid), with this size it gets removed so or so since it grew and did not burst (otherwise simple cysts are left alone if no symptoms, functioning ovaries do have cysts)
At hospital something non liquid was seen inside (the white bumps, solids and threads), was immediatly told, that it did not look benign like clot or benign tumor (dermoid) and if they could take my ovaries, uterus...etc out in one operation, if the quick slice test of ovary cyst sample during operation was positive from histology department.
Working in cytology at that time I said 'nope, you take the cyst with the tumor out, then it get's a propper histological slicing, staining and assessment, really knowing what it is and if taken out completely or what the margins were and then we go from there with further treatment'. But, but it would be a second operation. Well, yes, so be it. If it was not macroscopically looking like invasive cancer eating the uterus already, I did not want to rely on a quick test during operation.
And what was it? A BENING tumor, a dermoid/teratoma.
Why I say that:
There are indicators via blood test and ultrasound, if it was most likely benign or malignous, BUT it's still speculation.
It was the other way round for me, they prepared me for cancer and I stayed absolutely calm. Anyway it was going to come out so or so. Why should I freak out prior knowing what it was, being happy that it was found by accident, not that it was found. I was furious though how the message was broken to me without good reason.
So don't be frightend of anything prior knowing what is actually going on until a proper histology result comes in post surgery.
To have 'something white' in a cyst is pretty common and not weird.
If your gyn has seen normal tissue next to the cyst with solid inside, it is most likely benign growth. Also if she/he did assess the cyst wall thickness. Together with the CA125 picture she/he felt comfortable to put it rather into the benign speculation.
Which is good! But still only speculation, just...nothing at all to worry about now. It is state of the art to be sent to hospital for this and also I would just take it out.
Also consider: you got an ultrasound, yipee!
(in Austria we were entitled for an prophylactic ultrasound every year, in Australia there is nothing like that in place, one has to wait until a cyst twists or causes pain. Mine was found due to a prophylactic check up without symptoms. How about yours?)
So or so, you are in good hands, even if it was the worst outcome, you are there for treatment, help, not undiagnosed!
The glass is always half full when something is found.
Again: to differentiate malignant from benign ovarian cysts and masses, HISTOLOGY is the reliable and only method.
Sorry to say, but no worries, you need to have the surgery (laparoscopy I guess) = removal done and wait for histology.
All all the best!
PS: it would be very interesting if you could update us later please if you feel like sharing, what it was histologically. I am very nosy and somehow opening questions is done so much more often than closing them with a result, that could all teach us another experience and learn from.