Cancer of Unknown Primary With Presumptive Pancreatic Cancer Treated With FOLFIRINOX

A 52-year-old man was found to have an increase in carbohydrate antigen (CA)19-9. He underwent endoscopic ultrasound/fine needle aspiration (EUS-FNA) of the soft tissue shadow near the pancreas and was diagnosed with adenocarcinoma. The cancer was judged to be of unknown primary. Cancers of unknown primary make up 3-5% of malignant tumors, and it is difficult to determine the treatment policy. FOLFIRINOX’s efficacy in cancer of unknown primary is unclear. In this case, he received chemotherapy with FOLFIRINOX. After five cycles of treatment, the best effect was stable disease (SD). However, he died about 6 months after the onset of symptoms. Pathological anatomy after death revealed that the primary lesion was in the pancreas. FOLFIRINOX may be effective for cancers of unknown primary. Pathological anatomy is important to confirm the validity of treatment. It is important to consider giving chemotherapy if there is a presumed primary tumor even if the cancer is of unknown primary. J Med Cases. 2021;12(11):442-445 doi: https://doi.org/10.14740/jmc3812