Colorectal Adenocarcinoma Derived From Mature Cystic Teratomas: A Case Report With Review of the Literature.

Mature cystic teratomas (MCTs) are the most common benign ovarian germ cell neoplasms in women of reproductive age. Rarely, somatic malignancies arise from MCTs, the most common being squamous cell carcinoma. Adenocarcinomas are less common and colorectal adenocarcinomas are extremely rare. We present a case of somatic adenocarcinoma of colorectal type which may pose challenges in diagnosis and treatment. A middle-aged female presented to the Emergency Department with lower abdominal pain. CT scan revealed an 11 cm sharply demarcated left pelvic mass. Laparoscopy showed a left ovarian mass with torsion, a smooth external surface, and thick brownish contents. An intraoperative evaluation was consistent with an adenocarcinoma. Permanent histopathology revealed adenocarcinoma of colorectal phenotype with necrosis. Additional evaluation of the cyst showed benign colonic epithelial lining. The immunohistochemistry (IHC) profile of positive CDX2 and CK20 and negative PAX8, CK7, ER, and PR suggested a colorectal-type somatic adenocarcinoma arising from the MCT and was staged as IA, after negative endoscopic findings. Due to their rarity and atypical symptoms, distinguishing metastatic tumors from MCT-derived somatic malignancies is a challenging process. CT scan and serum tumor markers can be helpful but are not definite. Thorough clinical evaluation and proper staging are necessary after pathologic evaluation. Extensive sampling and IHC can further characterize the origin of the tumor. Diligent sampling and a high index of suspicion in this case clinched the correct diagnosis and clinical management. The patient is being treated for stage IA ovarian cancer as opposed to stage IV metastatic colorectal cancer.