Plasma Cells Out for a Swim! A Study on Myelomatous Involvement of Effusion Fluid and Cerebrospinal Fluid: A 10-Year Experience from a Tertiary Cancer Center

Background: Multiple myeloma (MM), a hematological malignancy marked by clonal plasma cells in the bone marrow, occasionally presents with myelomatous effusion-a rare condition with a median survival of <4 months. Central nervous system involvement (CNS-MM), characterized by plasma cell infiltration in the CNS, leptomeninges, or cerebrospinal fluid (CSF), is similarly rare and associated with dismal outcomes. Aims: To analyze the plasma cell involvement in body fluids and CSF in plasma cell neoplasms, correlating these findings with treatment strategies and patient outcomes. Materials and Methods: This retrospective study was conducted in the Oncopathology Department of a tertiary state cancer institute over 10 years (2013-July 2024). It included cases of plasma cell neoplasms with confirmed involvement of body cavity fluids or CSF. Data reviewed included epidemiological profiles, biochemical and hematological findings, immunohistochemistry results, treatment regimens, and follow-up information. Results: A total of 16 cases demonstrated neoplastic plasma cell involvement: 12 cases in pleural fluid and 4 cases in CSF. Of these, nine cases were diagnosed with MM, five cases with plasmacytoma, and two cases with plasma cell leukemia. Treatment included chemotherapy (10 patients), palliative radiotherapy (4 patients), combined palliative radiotherapy and chemotherapy (1 patient), and curative radiotherapy with chemotherapy (1 patient). Despite these interventions, the mean survival was only 2 months. Conclusion: Myelomatous involvement of effusion fluids and CSF is associated with a grim prognosis. These findings underscore the urgent need for multidisciplinary research and the development of innovative therapeutic strategies to improve outcomes for these patients.