Introduction Mature cystic teratoma (MCT) is the most common type of ovarian germ cell neoplasm, but occasionally it may undergo malignant change in any one of its elements. In this study, these rarely encountered tumors, occurring over a?period of 25 years, were studied. Material and methods A?retrospective, tertiary hospital-based study was carried out in all histopathologically diagnosed cases of MCT (230) of the ovary from January 1990 to December 2014. The clinicopathological features of malignant transformation (MT) in MCT of the ovary were retrieved from the archives of the Department of Pathology and were analyzed. Results Two hundred thirty (230) mature cystic teratomas of the ovary were found. MT was noted in eight of these cases, i.e. 3.5% of all the MCT. The mean age of the patients with MCT was 32.5 ±13.11 while the mean age of the patients with malignant transformation in MCT was 44.2 ±8.94 years. Grossly the mean size of the malignant teratoma was 11.7 ±2.7 cm, whereas it was 7.6 ±2.1 cm for mature cystic teratoma. Squamous cell carcinoma (SCC) was the most frequent MT seen in four out of eight cases, while one case showed an adenocarcinoma and the other a?malignant melanoma, and two cases had transitional cell carcinoma. Conclusions The rate of malignant transformation in MCT increases with age and is much higher in the postmenopausal age group. Moreover, although SCC is still the commonest, transitional cell carcinoma (TCC) may also develop not infrequently as malignancy apart from other rare differentiations such as adenocarcinoma or malignant melanoma in an MCT.
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