Malignant Transformation in a Mature Cystic Teratoma of the Ovary: A 5-year Descriptive Study

Background and Objective: Malignant transformation (MT) in mature cystic teratoma of the ovary (MCTO) is rare. This descriptive study primarily aims to determine the prevalence rate of MT in MCTO and describe clinicopathologic features, management, and prognosis of patients who developed this rare type of tumor and likewise deliver a review in the light of recent literature. Methods: This is a descriptive observational study of 22 patients with MT in MCTO at a Level 3 Tertiary Public Hospital in Baguio City, Philippines. The clinical and pathological records of each patient were reviewed. Descriptive statistics were used. Results: Between January 2016 to December 2020, of the 369 cases of mature cystic teratoma, 22 cases with malignant transformation were reported with an incidence of 6%. The mean age of diagnosis was 52 years, of which 70% are aged 50 years old and above. Fifty-nine percent (13/22) and 32% (7/22) of the cases were squamous cell carcinoma and mucinous adenocarcinoma, respectively. Very rarely, malignant transformations were carcinoid tumors (1) and follicular carcinoma (1). The most common reason for consult among patients is a palpable abdominal/pelvic mass (45.5%). Around 60% percent of cases have an elevated CA-125 value with a mean level of 180 U/ml. Seventy-two percent of cases with malignant transformation measured 10 cm or more with the largest mean diameter of 13 cm. Five patients underwent fertility-sparing surgery. Fourteen had staging procedures. Twelve patients were at Stage I. Three were at Stage II. Four and three patients were at Stage III and IV, respectively. Ten patients received adjuvant platinum-based chemotherapy and nine patients warrant no treatment after surgery. The median survival time is 14 months. Conclusion: Although not common, malignant transformation in MCT should be considered in older patients with large tumor sizes and elevated CA-125 assessed as MCT in preoperative and intraoperative assessment. This ovarian malignancy suggests an aggressive behavior but complete resection with systematic staging and indicated adjuvant platinum-based chemotherapy may improve survival.