Introduction: Mature ovarian cystic teratoma is a cystic fatty tumor. Presence of floating fat balls in an ovarian cystic teratoma looking like a "sack of marbles" on magnetic resonance imaging (MRI) is a rare finding.
Patient concerns: Herein, we report a 38-year old woman who was admitted to our hospital presenting with an abdominal mass and abdominal pain.
Diagnosis: Ultrasonography revealed a giant cystic mass in the pelvis; T1-weighted MRI revealed multiple spherical signals in the lesion.
Interventions: She underwent exploratory laparotomy and was histopathologically diagnosed with benign cystic teratoma.
Outcomes: Finally, the patient recovered after operation. Until December 2018, she had been still healthy without recurrence of tumors.
Conclusion: The aim of this case report was to present "sack of marbles" appearance on MRI, which will impress other doctors and improve the diagnosis of such diseases.