Adenocarcinoma With Intestinal and Pancreatobiliary Features Arising From a Sacrococcygeal Teratoma in an Adult Female: A Case Report.

Sacrococcygeal teratomas (SCTs) are rare in adults, and malignant transformation within these tumors is exceedingly uncommon. The risk of malignant transformation among adults can vary between 1% and 12% and increases over time with the endopelvic location. Here, we present a case of invasive adenocarcinoma with intestinal and pancreatobiliary features arising from a preexisting SCT in a 64-year-old female. The patient presented with a rapidly enlarging sacral mass and purulent drainage decades after the excision of a congenital lump in the sacral region. Imaging revealed a lytic lesion involving the coccyx and sacrum, accompanied by an ill-defined soft tissue mass. Histological evaluation confirmed adenocarcinoma with dual intestinal and pancreatobiliary differentiation originating from a preexisting SCT with focal involvement of the resection margin. Postoperatively, a multidisciplinary team recommended FOLFIRINOX chemotherapy followed by completion excision surgery. This case contributes to the limited literature on adult SCTs with malignant transformation, highlighting the critical need for timely and comprehensive management. Multidisciplinary evaluation, complete surgical resection, and tailored adjuvant therapy are essential to improving patient outcomes in such rare cases.