Bilateral breast plasmacytomas in a male patient with relapsed multiple myeloma: A case report

Breast involvement in multiple myeloma (MM) is rare, and bilateral plasmacytomas in male patients are exceptionally uncommon. We report a 73-year-old man with relapsed IgG kappa MM who presented with new-onset gynecomastia and multiple palpable masses in both breasts and axillae. Contrast-enhanced mammography demonstrated multiple enhancing bilateral breast masses, with heterogeneous enhancement on recombined images and corresponding hypoechoic masses on ultrasound. Core biopsy confirmed plasma cell neoplasm (CD138+, CD56+, kappa-restricted). CT revealed disseminated extramedullary disease involving the liver, retroperitoneum, pancreas, and bones. Despite supportive care, the patient deteriorated rapidly and died 1 month later. This case highlights the diagnostic value of contrast-enhanced mammography in detecting multifocal breast plasmacytomas and underscores the clinical significance of bilateral extramedullary relapse in male MM.