Uncommon initial presentation of a gastric mass in a patient with primary plasma cell leukemia: a case report

Extramedullary infiltration is a recognized manifestation of primary plasma cell leukemia (pPCL); however, presentation as a gastric mass is rarely reported. This report describes a rare case of pPCL complicated with prostate cancer, initially presenting as a gastric mass, and outlines the pathogenic mechanisms and clinical management course. A 68-year-old man presented with intermittent epigastric pain. Contrast-enhanced abdominal computed tomography (CT) revealed a gastric mass measuring 97 mm × 131 mm × 63 mm, subsequently confirmed as an extramedullary plasmacytoma on pathological examination. Bone marrow biopsy and peripheral blood immunophenotyping established the diagnosis of pPCL with gastric involvement. In view of an elevated prostate-specific antigen level, a targeted prostate biopsy was performed, confirming concomitant prostate cancer. The patient received three cycles of the Dara-RVD regimen for pPCL, along with leuprolide acetate and bicalutamide for prostate cancer. Follow-up evaluation demonstrated partial remission of pPCL. Additional case accumulation and further investigation of pathogenic mechanisms are warranted to optimize diagnostic approaches and improve therapeutic outcomes.