Serum CA19.9 levels are commonly elevated in primary ovarian mucinous tumours but cannot be used to predict the histological subtype -- Journal of Clinical Pathology

Conclusion: Preoperative CA19.9 levels cannot be used to predict whether a suspected ovarian mucinous tumour is benign, borderline or malignant. Markedly elevated serum levels (>1000 U/ml) may be found in benign mucinous neoplasms as well as in borderline and malignant tumours.