How can radiologist tell the difference from a malignant and benign ovarian cyst on ultrasound. And is the sympthoms the same.

Imaging findings. Radiologist can simply raise suspicion of malignancy based on imaging findings.These may include internal separation , solid component and presence of fluid in the pelvis. This may alarm the gynecologist to further investigate the cyst. Final diagnosis is often based on surgical and histopathological evaluation.
TUMORS. Whether benign or malignant, are solid. Cysts are fluid filled. Radiologists will read these as suspicious for malignancy, depending on the tissue being ultrasound. If solid, ultimately a biopsy or removal is the method that determines for certain whether cancerous or not, when indicated. It is all about probabilities and appearance when it comes to radiological interpretations.