Bilateral cystic-appearing mucinous ovarian tumours can either be primary ovarian or secondary from extra-ovarian primary sites predominantly gastrointestinal tract like appendix, pancreas, colon, stomach, biliary tract and gall bladder. The differentiation between primary ovarian lesions and ovarian metastasis from distant primary is significant as it directly influences the patient’s management and prognosis.

We report a case of an occult low-grade appendiceal mucinous neoplasm (LAMN) which manifested primarily clinico-radiologically as bilateral large mucinous cystic ovarian tumours. Reviewing the literature, we found that at times it becomes very challenging for clinicians and radiologists to pre-operatively diagnose bilateral ovarian lesions as metastatic, owing to the absence of an evident extra-ovarian primary source on imaging.

This especially holds in cases of primary appendiceal mucinous neoplasms, which remain occult clinically and on imaging, with their first clinical–radiological manifestation usually being bilateral predominantly cystic ovarian lesions.