{Reference Type}: Case Reports {Title}: Malignant Transformation of an Ovarian Mature Cystic Teratoma to a Malignant Melanoma. {Author}: Rathore R;Ahuja S;Nakhro N;Punhani P;Zaheer S; {Journal}: Indian J Surg Oncol {Volume}: 15 {Issue}: 2 {Year}: 2024 Jun 暂无{DOI}: 10.1007/s13193-024-01896-z {Abstract}: Ovarian mature cystic teratomas comprise tissue derived from all three germ layers and constitute 10-20% of all ovarian neoplasms. Malignant transformation of mature cystic teratomas (MCT) is very rare with an incidence of 0.17-2%. The most frequently reported malignancies include squamous cell carcinoma and adenocarcinoma. Herein, we describe a case of a 56-year-old female who presented with abdominal pain and underwent total abdominal hysterectomy with bilateral oophorectomy and omentectomy for a ruptured dermoid cyst. Histological examination showed nests of pleomorphic cells with prominent nucleoli and melanin pigment in the background of a mature cystic teratoma. These cells showed immunoreactivity for Melan-A and HMB-45, thus confirming the diagnosis of malignant transformation of a mature cystic teratoma to a malignant melanoma.