Primary Mature Cystic Teratoma of the Retroperitoneum Presenting as a Suprarenal Mass in an Adult Patient: A Case Report

Introduction: Primary retroperitoneal mature cystic teratomas (PRPMCT) are uncommon in adults. They typically occur in infants under six months old and young females. So far, some limited case reports have been documented in the literature. This case report presents a rare case of an adult patient with PRPMCT aged over 30 years. Case Presentation: The patient was a 34-year-old female with PRPMCT in the site of the left adrenal gland and abdominal discomfort. Computed tomography (CT) scan revealed a 66 mm hypodense lesion with fat attenuation and calcification in the left retroperitoneum. Laparotomy with resection of the retroperitoneal (RP) lesion was done. Gross examination showed a solid multicystic mass measuring 8x6.5x6 cm. Histopathologic examination revealed a neoplastic tissue composed of mature osseous and cartilaginous tissue associated with stratified squamous epithelium and lumens lined by ciliated columnar epithelium, and the diagnosis was mature cystic teratoma. The patient had an uncomplicated postoperative course without recurrence after seven months of follow-up. Conclusions: PRPMCT in adults is extremely rare. RP metastasis of primary gonadal teratoma and non-functioning adrenal tumors should be excluded first. Due to the diagnostic difficulty of posterior peritoneal teratoma with radiological imaging and its risk of malignancy, surgical resection would be the most effective diagnostic and therapeutic option. Complete resection of the mass is important to judge the existence of immature and solid components that require a long-time follow-up because of the increased risk of malignancy.