Background: Collision tumor is a clinically rare disease, it is defined as two or more primary tumors from different tissues occurring at the same anatomical site. Ovarian collision tumor is more rare.
Case presentation: A patient was hospitalized with a pelvic mass. The CA125 level was 53.46U per milli liter (normal range, 0 to 30u/ml). Another patient was hospitalized with lower abdominal pain and no apparent hormonal abnormalities. Ovarian lesions were found in both patients after examination, and postoperative pathology showed that both patients were ovarian collision tumors.
Conclusion: Collision tumor composed of mature cystic teratoma, follicular membranous cell tumor and serous cystadenoma was first reported. The biological behavior of collision tumor is different due to its different components. Accurate diagnosis is of great significance to treatment.