Persistent elevation of CA 19-9 levels in a patient with an extended retroperitoneal dermoid

CA 19-9 has been established as sensitive tumor marker in a variety of malignant diseases, especially in carcinomas of the exocrine pancreas. The specificity of CA 19-9 is limited by many benign diseases causing abnormal values. A case of a patient with a retroperitoneal dermoid showing high serum levels of CA 19-9 will be described. The patient suffered from a large retroperitoneal mass (7 x 6 x 9 cm). A CT-guided fine needle biopsy of the tumor was performed and the histology was compatible with a benign dermoid. The CT-scans of the abdomen showed also the typical features of a dermoid. Tumor markers and lab counts stayed in the normal range except CA 19-9, which was constantly elevated with value between 131 and 329 U/ml. A benign or malignant disorder was excluded. An immunoscintigraphy and a SPECT with a I-131-labeled monoclonal antibody against CA 19-9 revealed the retroperitoneal mass as the source of the CA 19-9 elevation. This is the first case described in English scientific literature of a retroperitoneal dermoid (benign teratoma) as a source of a persistently elevated level of CA 19-9.