Retroperitoneal Leiomyosarcoma with Elevated CA 19-9.

Leiomyosarcomas are malignant soft tissue tumors that can arise nearly anywhere in the body. These tumors may rarely originate within the retroperitoneum and may be found incidentally or present with nonspecific symptoms due to mass effect on abdominal or pelvic organs. The presentation of a leiomyosarcoma with a massively elevated CA 19-9 level is exceedingly rare with only one other report in the literature. This presentation makes for a diagnostic challenge, especially in the presence of metastatic disease to adjacent organ systems, and often requires a tissue sample obtained with core needle biopsy to make a definitive diagnosis.