This report presents the case of squamous cell cancer (SCC) originating from a mature cystic teratoma (MCT) diagnosed in pregnant women, in whom retroperitoneal spread to para-aortic lymph nodes was confirmed as the only evidence of extraovarian disease in a relatively short time after primary tumor excision. The 35-year-old multipara was diagnosed in early pregnancy with an ovarian tumor. The patient qualified for elective caesarean section with left ovarian cystectomy. Pathological result proved SCC in MCT and the patient underwent debulking surgery without total pelvic and para-aortic lymphadenectomy. Final staging confirmed ovarian malignancy FIGO IA, and no adjuvant treatment was recommended. Early imaging examination during routine follow-up demonstrated enlarged para-aortic lymph nodes and the patient qualified for total pelvic and para-aortic lymphadenectomy. Postoperative pathology result confirmed metastases in para-aortic lymph nodes and standard adjuvant chemotherapy was administered.