Low‐grade mucinous neoplasm arising from a recurrent mature sacrococcygeal teratoma

Extragonadal germ cell tumours (GCTs) arises outside the testes or ovaries and can occur in retroperitoneum, mediastinum and sacrococcygeal area.1, 2 Sacrococcygeal teratomas (SCTs) are most common in the paediatric population and account for 40%–70% of teratomas.3 The site of origin, maturity of the tissue and the age at which patients present can predict the likely malignant potential of the teratoma.3-6 Here we present a case of a recurrent SCT with mucinous neoplasm that presented as a cystic pelvic mass. A seventy-seven-year-old female with a history of having a SCT surgically resected as a child, was being managed with a vaginal pessary for a symptomatic uterine prolapse. She developed dysuria and urinary frequency and during a routine pessary exchange procedure, the gynaecologist noticed a palpable soft tissue mass in the posterior wall of the vagina. A CT (computed tomography) of the chest abdomen and pelvis, pelvic MRI (magnetic resonance imaging) and PET (positron emission tomography) were performed. A large multiloculated cystic pelvic mass was identified with peripheral calcification posterior to the rectum and uterus, extending inferiorly into the ischiorectal fossa bilaterally and abutting the pelvic sidewall (Fig. 1). The PET scan showed incomplete areas of peripherally located moderately intense metabolic activity (Fig. 2). There were no distant metastases. In an attempt to relieve pressure symptoms, the cystic mass was drained via the vagina. Cytology of the cystic fluid was consistent with a mucinous neoplasm. The patient underwent resection of the presacral tumour with an en-bloc abdominal perineal resection of the rectum (inseparable from tumour), hysterectomy and bilateral salpingo-oophorectomy with a flap closure. The histopathology confirmed a mature teratoma in the pelvic soft tissues containing mature cartilage, fat and ependymal or neuroepithelial cells with a low grade mucinous neoplasm. The surgical margins were clear (Fig. 3). The patient recovered well post-operatively without complication. No further adjuvant treatment was required. Malignant transformation of a mature teratoma is rare, ranging from 1% to 12%, with the potential to arise from a number of different tissue types making diagnosis and treatment challenging.4, 5 In the literature, squamous cell carcinoma is the most common malignancy arising from a teratoma, accounting for 80% of the cases, followed by adenocarcinoma and sarcoma.4, 5, 7 Previous cases of mucinous tumours developing from SCT have been reported and similarly managed with surgical resection.8, 9 Surgical resection is the preferred treatment option for SCT in order to determine the composition and maturity of tissue elements and to rule out malignancy.4 Malignant histology, incomplete surgical resection, and failure of en bloc resection of the coccyx are associated with a high risk of recurrence with an overall recurrence rate of approximately 10% for mature teratomas and 20% for immature teratomas.4, 10 Therefore, close surveillance with regular imaging is crucial for long term follow up of these patients. There is no current consensus of the management of malignant transformation of SCT and no specific guidelines as it depends on the tissue of origin. However surgery, chemotherapy, or radiotherapy should be considered according to the histological type.4 In patients presenting with a pelvic cystic mass on a background of teratoma, there should be high index of suspicion of malignant transformation. We are grateful to the patient who consented to use the clinical information and images. The authors certify that they have obtained all appropriate patient consent. Ahmed Nada: Writing – original draft; writing – review and editing. Yui Kaneko: Writing – original draft; writing – review and editing. Corina Behrenbruch: Conceptualization; writing – review and editing. Michael Johnston: Conceptualization; writing – review and editing.