Ovarian mature cystic teratoma with papillary thyroid carcinoma and carcinoid components invading the adjoining sigmoid colon: A case report
Authors: Liu Jixuan , Ni Jinsong , Liu Yafang 
Published: May 2023

Abstract
Background: Malignant transformation of ovarian mature cystic teratoma rarely develops, especially when multiple malignant components simultaneously occur.
Case presentation:A 47-year-old woman presented with a 12-month history of intermittent abdominal distension and pain along with bloody stool for 3 weeks. Abdominal computed tomography revealed a cystic mass in the right ovary adjacent to the colon. Additionally, fluids were observed in the colon cavity . Colonoscopy showed a protuberant mass on the surface of the sigmoid colon covered with blood . Considering the large size of the colonic mass and the undetermined diagnosis of the mass, the patient underwent laparoscopic partial colectomy, hysterectomy, and bilateral appendage resection.Grossly, the ovarian cyst was connected to the colon wall, and the cut surface of the colon tumor was cystic and contained mucus. Histopathological examination revealed that the surface of colonic lesions was the granulation tissue, and the lower part was composed of fibrous stroma and mucinous cyst. The cyst wall was covered with columnar cells and contained abundant intracellular mucin. No nuclear atypia was observed. The lesions penetrated the entire intestinal wall and connected with ovarian cysts. Mucus, lipids, and hair could be observed in the ovarian cyst cavity. Histopathological examination showed that the cyst wall was lined with stratified squamous epithelium, and the sebaceous glands could be observed in the fibrous stroma of the cyst wall. Thyroid follicular components could be found in the surrounding area, and some cells were arranged in a chrysanthemum-like cluster . Under high magnification, the nuclei of these cells were characterized as pepper-salt-like . In another area, the typical papillary structure of papillary thyroid carcinoma and the formation of multiple cysts containing mucus were observed; some of which were lined with columnar epithelium containing goblet cells . Under high magnification, the nuclei of these papillae were crowded, ground glass-like, with nuclear grooves. Notably, no malignant tumor components were observed in the colon wall and colon polyps, which are only composed of benign mucinous epithelium. Based on these findings, the patient was suspected of ovarian mature cystic teratoma, which contained mucinous cysts, carcinoids, goiters, and papillary thyroid carcinoma. Moreover, mucinous cysts involved the colon wall and formed a polypoid appearance. At the time of this writing, 6 months had passed since treatment completion, without clinical or histological evidence of recurrence.
Conclusion: Herein, we present a rare case of malignant ovarian mature cystic teratoma, including mucinous cysts, goiters, papillary thyroid carcinoma, and carcinoids. The tumor remarkably invaded the intestinal wall and formed a benign polypoid appearance, suggesting the occurrence of this rare tumor type should be considered when intestinal polyps are found during gastrointestinal endoscopy.