Monoclonal Gammopathy with Isolated CA 19-9 Elevation: A Rare Case

ABSTRACT Objective: CA 19-9 is a tumor marker used in the diagnosis of pancreatic and gastrointestinal cancers, but its isolated elevation can also be seen in benign conditions. Method and Result: A 48-year-old man presented with complaints of abdominal pain and malaise and a CA 19-9 level of 500 U/mL. Imaging studies did not show malignancy. Serum protein electrophoresis revealed IgG class monoclonal protein and bone marrow biopsy was normal. The patient was diagnosed with monoclonal gammopathy of unknown significance. Six months later, CA 19-9 level decreased to 300 U/mL and no malignancy developed. Conclusion: Isolated CA 19-9 elevation may be associated with causes other than malignancy and may be related to monoclonal gammopathy. In such cases, careful evaluation and unnecessary procedures should be avoided. Keyswords: Monoclonal Gammopathy, CA 19-9, Diagnostic Difficulty, Tumor Marker.