Introduction/Background Mature Cystic Teratoma (MCT), the so-called dermoid cyst, is the most common germ cell tumor of the ovary. Among of all ovarian tumors, 10–20% of them is dermoid cyst.(1) It is usually encountered in the reproductive ages. Although asymptomatic cases are not rare, it mostly presents itself with abdominal pain and mass .(1) MCT is a benign tumor but occasionally ( 1–2%) may show malignant transformation. Malignant forms are usually seen in older ages.(1,2)The most commonly observed malignant tumor is squamous cell carcinoma ( SCC) being at rate of 70–80%.(1) Sometimes these tumors may spread by local invasion or peritoneal seeding to adjacent organs and may cause related symptoms. (3).

Results The case is 40 years old. Until now she stated that she had no sexual life. The patient had undergone unilateral salpigo-oophorectomy and intestinal operation with fibrous bridge dissection. The pathologic result is squamous cell carcinoma arising in the dermoid cyst. At the beginning of the operation endometrial currettage was performed. Subsequently, dissection of the small intestine adhesions with the resection of the ileum in the form of the conglomerate mass. The anastomosis was completed by ileo- jejunal stapler. Total abdominal hysterectomy with unilateral salpigo-oophorectomy was added. Since the other adnex was removed in the previous operation. Additionally, partial peritonectomy with pelvic and paraaortic lymphadenectomy were done . There was no residual macroscopic tumor left behind. As an adjuvant treatment, chemotherapy with cisplatin and paclitaxel was given and the patient is under periodic follow-up.

Conclusion Although MCT is a benign tumor, it should be kept in mind that occasionally malignant transformation ( principally SCC ) may arise in this tumor. There is no method or sign to definitely predict malignant transformation, large MCT seen in older ages with particularly elevated CEA levels is suspicious for malignant transformation.