Myelomatous Ascitis, a Rare Presenting Symptom of Multiple Myeloma

Abstract Introduction/Objective In 2022, plasma cell neoplasms accounted for approximately 1.8% of all new cancers in the United States with an estimated 34,470 new cases of multiple myeloma. Diagnosis is often straight forward in ~80% of cases by performing serum protein electrophoresis (SPEP), serum immunofixation (SIFE), and/or urine immunofixation (UIFE) with M-spike quantification. The diagnostic challange is in the remainder of asymptomatic myeloma cases (~20%) which are found incidentally. Specialized laboratory technicians are often the first step in identifying plasma cells in body fluids and/or peripheral blood smears. These incidental findings on routine labs, paired with the keen eye of a specialist, are one of the first steps in early detection of multiple myeloma. Methods/Case Report A 62 year-old male, originally from Cambodia, presented to an outside hospital emergency department with abdominal distention and pain. His past medical history was significant for dialysis-dependent end- stage renal disease and insulin-dependent diabetes mellitus type 2. Abdominal CT showed ascites with no other diagnostic findings. Cardiac, renal and hepatic etiologies of ascites were ruled out. Body fluid analysis of the ascites in the Clinical Pathology laboratory revealed numerous plasma cells. Cytologic examination, after consultation with Clinical Pathology, also revealed numerous plasma cells. Subsequent SPEP and SIFE disclosed an IgA lambda monoclonal protein. A diagnosis of multiple myeloma was confirmed by bone marrow biopsy with FISH studies. Results showed several high-risk abnormalities including translocations of 4::14, 14::16, and 14::20, denoting a “triple hit” multiple myeloma. Results (if a Case Study enter NA) NA Conclusion Plasmacytosis in ascites is an extremely rare initial presentation for multiple myeloma. With only a few cases reported in the literature, many technicians and pathologists might easily overlook plasma cells on routine cytology, especially with normal imaging and no previous diagnosis of myeloma. In this case, flagged peritoneal fluid by a skilled medical laboratory technician was key to making a diagnosis. Without any signs of a plasmacytoma or lytic bone lesions on imaging, a normal CBC with non-specific labs, and an unsuspecting surgical pathology report, multiple myeloma was not on the differential. Fast interdepartmental consultation, communication, and teamwork between surgical pathology and clinical pathology, lead t