We present an unusual case of a 52-year-old man diagnosed with multiple myeloma 7 years ago, with osteolytic lesions of the cranium, vertebrae and pelvic bone. Treatment included radiation therapy, chemotherapy and bisphosphonates, followed by autologous stem-cell transplantation. After that, he was treated with maintenance immunotherapy to maintain disease remission. Three years ago, the patient presented with painless swelling of the left testicle. Ultrasonography revealed an enlarged inhomogeneous left testicle, with increased vascularity. After biopsy (a plasmacytoma was diagnosed) and failed radiotherapy, radical orchiectomy was performed. Six months ago, the patient had an initial increase in volume of the right testicle; ultrasonography showed a modest increase in testicular volume (approximately 4 cm) surrounded by an anechoic septated fluid collection diagnosed as hematocele. Four months ago, ultrasound showed a further increase in testicular volume (approximately 5 cm), with an unchanged fluid collection around the testicle. A further control after 2 months showed further volume increase (approximately 7 cm) of the testicle, which appeared inhomogeneous and hypervascularized (Figs.