Pediatric puzzle: Large ovarian dermoid cyst and markedly elevated CA 19-9 in an 8-year-old.

Background: Mature cystic teratomas, also known as dermoid cysts, are the most prevalent form of ovarian germ cell tumors. While they typically manifest in women of reproductive age, they can also occur in pediatric patients. These tumors are generally benign and comprise a diverse array of tissue types. However, large lesions, particularly those exceeding 10 cm in diameter, are infrequent and can present diagnostic and therapeutic challenges. Notably, elevated tumor markers, such as cancer antigen 19-9 (CA 19-9), are not commonly associated with mature cystic teratomas, rendering this case particularly unusual. Case presentation: The clinical case involved an 8-year-old female patient who presented with an exceptionally large ovarian teratoma, measuring 13 × 12 cm. While the prepubertal presentation of such tumors is not uncommon, the remarkable size of the lesion was an extraordinary occurrence. Preoperative evaluation revealed markedly elevated levels of CA 19-9, a tumor marker, at 297 U/mL-an atypical finding for mature cystic teratomas. Imaging studies identified a complex cystic adnexal mass, indicative of a teratoma. Consequently, a laparotomy was performed, revealing an intact, benign lesion that was successfully resected via cystectomy, with preservation of the ovary. Histopathological examination confirmed the diagnosis of a mature cystic teratoma, without any evidence of malignant transformation. Notably, following the surgical intervention, the elevated CA 19-9 levels normalized, suggesting a potential association between the teratoma and the abnormal tumor marker levels. Discussion: This report delineates the surgical management and clinical course of an exceptionally large ovarian teratoma in a pediatric patient with abnormal preoperative tumor markers. Despite atypical features, the excellent prognosis following fertility-sparing resection underscores the significance of conservative treatment in young females. Conclusion: This case highlights the occurrence of a large mature cystic teratoma with elevated CA-19-9 in a pediatric patient with no complications such as torsion, rupture, or malignancy. The elevation in CA-19-9 likely relates directly to the teratoma itself. A conservative, fertility-sparing surgical approach proved effective, emphasizing the importance of careful preoperative evaluation and management in similar cases.