When two benign ovarian pathologies collide: an incidental bilateral collision tumour of mature cystic teratoma and endometrioma

Katherine Atallah, Atallah K, Khalid Atallah, Antonio Al Hazzouri, Al Hazzouri A, Saliba K, Kaity Saliba, Attieh P, Philippe Attieh, Azizi L, Lamia Azizi, Karam Karam, Karam K, Emile Dabaj, Dabaj E
European journal of case reports in internal medicine · 2026 · vol. 13(3) , pp. 006209 · doi:10.12890/2026_006209 · PMID:41809961 · PMC12971047 · W7131823445
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⚙ AI-generated summary by gemini-2.5-flash-lite, 2026-06-07 ⓘ

This case report describes an incidental bilateral collision tumor of mature cystic teratoma in one ovary and endometrioma in the contralateral ovary, highlighting diagnostic challenges and the need for histopathological confirmation.

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⚙ AI-generated deep summary by claude@2026-06, 2026-06-07 · read from full text ⓘ

This paper reports a rare ovarian “collision tumor” scenario involving two distinct benign pathologies, focusing on an incidental case of bilateral masses in a 27-year-old woman. Pelvic MRI identified bilateral adnexal lesions, and surgical exploration with histopathology found a mature cystic teratoma in one ovary and an endometrioma in the contralateral ovary, with the patient presenting no significant gynecologic symptoms. The authors emphasize that preoperative imaging has limitations in detecting synchronous ovarian pathologies, but they do not provide broader clinical cohorts beyond this case. This paper is centrally about endometriosis — it documents a contralateral endometrioma as part of a bilateral collision of an endometrioma with a mature cystic teratoma.

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Abstract

Ovarian collision tumours are rare entities defined by the coexistence of two histologically distinct neoplasms, most commonly reported within the same ovary, while bilateral involvement is extremely uncommon and often under-recognised. Endometriomas are common benign ovarian lesions in women of reproductive age and may be asymptomatic or incidentally detected, whereas mature cystic teratomas are the most frequent ovarian germ cell tumours and are often discovered unintentionally during imaging or surgery. We report the case of a 27-year-old woman in whom adnexal lesions were incidentally identified, with no significant gynaecologic symptoms at presentation. Pelvic magnetic resonance imaging (MRI) showed bilateral ovarian masses, and surgical exploration revealed distinct ovarian lesions involving both ovaries. Histopathological examination confirmed a mature cystic teratoma in one ovary and an endometrioma in the contralateral ovary. This unusual and incidental bilateral presentation highlights the limitations of preoperative imaging in detecting synchronous ovarian pathologies and underscores the importance of thorough intraoperative assessment and definitive histopathological evaluation. Increased awareness of this rare entity is essential to optimise surgical management, fertility preservation and follow-up. LEARNING POINTS: Ovarian collision tumours are rare pathological entities, and presentations involving histologically distinct tumours in different ovaries are extremely uncommon.This case adds to the limited literature by illustrating an atypical and largely incidental presentation with non-specific symptoms.Such variability in clinical and radiologic presentation underscores the diagnostic complexity of these tumours and the potential for under-recognition.Although advanced imaging, particularly MRI, may provide important diagnostic clues, definitive diagnosis relies on a comprehensive histopathological assessment.Awareness of this unusual presentation is crucial, as early recognition of bilateral but distinct ovarian tumours can influence surgical planning, fertility-preserving strategies and follow-up, ultimately improving individualised patient care.
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Keywords

Ovarian collision tumours, mature cystic teratoma, endometrioma

Abstract

Ovarian collision tumours are rare entities defined by the coexistence of two histologically distinct neoplasms, most commonly reported within the same ovary, while bilateral involvement is extremely uncommon and often under-recognised. Endometriomas are common benign ovarian lesions in women of reproductive age and may be asymptomatic or incidentally detected, whereas mature cystic teratomas are the most frequent ovarian germ cell tumours and are often discovered unintentionally during imaging or surgery. We report the case of a 27-year-old woman in whom adnexal lesions were incidentally identified, with no significant gynaecologic symptoms at presentation. Pelvic magnetic resonance imaging (MRI) showed bilateral ovarian masses, and surgical exploration revealed distinct ovarian lesions involving both ovaries. Histopathological examination confirmed a mature cystic teratoma in one ovary and an endometrioma in the contralateral ovary. This unusual and incidental bilateral presentation highlights the limitations of preoperative imaging in detecting synchronous ovarian pathologies and underscores the importance of thorough intraoperative assessment and definitive histopathological evaluation. Increased awareness of this rare entity is essential to optimise surgical management, fertility preservation and follow-up.

References

- Tanoglu FB, Karakus SS, Karakus R, Akgun N, Ustun YE, Ates S, et al. Endometrioma and mature cystic teratoma as collision tumors of the ovary: a case series and literature review. Int J Gynecol Pathol 2026;45:142–151. doi: 10.1097/PGP.0000000000001147 - Cong L, Wang S, Yeung SY, Lee JHS, Chung JPW, Chan DYL. Mature cystic teratoma: an integrated review. Int J Mol Sci 2023;24:6141. doi: 10.3390/ijms24076141 - Matalliotakis M, Matalliotaki C, Tsakiridis I, Dagklis T, Michos G, Romanos A, et al. Co-existence of Ovarian Teratomas With Other Gynecological Tumors. Cureus 2024;16:e58068. doi: 10.7759/cureus.58068 - Vaduva CC, Dira L, Boldeanu L, Serbanescu MS, Carp-Veliscu A. A narrative review regarding implication of ovarian endometriomas in infertility. Life (Basel) 2025;15:161. doi: 10.3390/life15020161 - Matalliotakis M, Matalliotaki C, Zervou MI, Krithinakis K, Goulielmos GN, Kalogiannidis I, et al. Retrospective evaluation of pathological results among women with ovarian endometriomas versus teratomas. Mol Clin Oncol 2019;10:592–596. doi: 10.3892/mco.2019.1844 - Shams F, Ahmed S, Habib M, Anjum AS. Endometrioma coexisting with mature cystic teratoma in a single ovary: a rare presentation. J Ayub Med Coll Abbottabad 2024;36:447–450. doi: 10.55519/JAMC-02-12623 - Song J, Martin C. A rare case of a large composite endometrioma–mature cystic teratoma: the importance of surgical treatment and pathologic diagnosis. Reprod Med 2024;5:280–287. doi: 10.3390/reprodmed5040024 - Rokhgireh S, Mehdizadehkashi A, Tahermanesh K, Gorginzadeh M. Association of endometrioma with ovarian teratoma and mucinous cystadenoma in a patient diagnosed with endometriosis: a case report. World J Obstet Gynecol 2019;8:8–12. doi: 10.5317/wjog.v8.i2.8 - Balint O, Secosan C, Pirtea L, Grigoras D. Rare association between an endometrioma and a mature cystic teratoma on the same ovary in a postmenopausal woman: a case report and review of literature. J Gynecol Womens Health 2020;18:555982. doi: 10.19080/JGWH.2020.18.555982 - Darouichi M, Tille JC, Dubuisson J, Jovanovic S. Coexistence of mature cystic teratoma and endometrioma in an ovarian cyst. J Dig Disord Diagn 2017;1:11–16 doi: 10.14302/issn.2574-4526.jddd-17-1498 Views: 851 HTML downloads: 154 PDF downloads: 277 Published: 2026-02-23 Issue: Vol. 13 No. 3 (2026) (view) This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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