Introduction/Background Mature cystic teratomas are the most common type of benign ovarian tumors. However, their malignant transformation is uncommon and occurs in 1.5–2% of dermoid cysts [1, 2]. We present a very rare case of early-stage ovarian adenocarcinoma resulting from malignant transformation of dermoid cyst.

A fourty-seven-years-old female patient was admitted to the Hospital due to acute abdominal pain caused by an unlarge tumor located in the pelvis and abdominal cavity. Transvaginal sonography and computed tomography revealed a 15 cm in diameter liquid cyst with one solid part 2.5 cm in diameter, without pathological vascularization. CA125, CEA, AFP, Ca 19–9 were within normal range. Due to acute condition of the patient, an immediate laparotomy was performed, which consisted of right adnexectomy and left salpingectomy.

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Abstract #592 Figure 1

Ovarian adenocarcinoma. H+E. 40x.

Results Pathology examination revealed ovarian teratoma with the component of adenocarcinoma of medium differentiation stage (pT1a NX, FIGO IA) [figure 1]. After a month, the patient underwent secondary intervention for careful restaging. No signs of cancer or metastatic disease were observed. She remains under routine oncological follow-up more than a year with favorable survival prognosis.

Conclusion Malignant transformation of the mature dermoid cyst is a rare entity and it is truly difficult to detect neoplastic transformation especially when the diagnostic imaging and oncological markers are within the normal ranges. Ovarian cyst sized above 10 cm in diameter, with suspected solid components, should be very carefully managed with special oncological care.

Disclosures The authors report no conflicts of interes.