Endometrioma and Mature Cystic Teratoma as Collision Tumors of the Ovary: A Case Series and Literature Review.

The simultaneous presence of distinct histologic types of ovarian cysts in a single patient, known as "collision tumors," presents a clinical challenge. In this study, we report 19 new cases of ovarian collision tumors involving both endometriomas and mature cystic teratomas (MCTs), and we review their characteristics alongside 30 previously reported cases. Among the total of 49 patients, the mean age was 32.28±8.07 yr, with 66.67% being nulliparous. The most common clinical symptom was abdominal pain (55.10%), while 12.24% were diagnosed incidentally. Primary infertility was identified in 14.28% of patients. Of the 44 cases with available surgical data, 32 underwent cystectomy and 12 underwent oophorectomy. In the 19 newly reported cases, 10 patients desired fertility preservation, yet only one achieved spontaneous pregnancy after surgery. Although both endometriomas and MCTs are benign ovarian lesions, their coexistence is rare. Tissue diagnosis is essential to exclude malignancy and guide follow-up, but preserving ovarian reserve is equally critical. Recognizing the presence of collision tumors can help physicians utilize radiologic methods more effectively and adopt a more proactive approach, safeguarding the future fertility and quality of life of these patients.