A 70-year-old man underwent salvage therapy for multiple myeloma (MM). While on maintenance immunotherapy he developed a sternal plasmacytoma. After the fifth cycle of treatment, he developed swelling, erythema, and pain in his right testis.
The main differential diagnoses for those symptoms are infections and tumors; infection is more common, so his clinicians at Indiana University School of Medicine presumed orchitis and started him on IV antibiotics. The pain resolved, but the swelling persisted after the antibiotic course. The clinicians turned to biochemical marker screening for germ cell tumors, but those were negative. Serial ultrasound imaging, which they had begun during his admission, remained unchanged.
Meanwhile, the patient’s chemotherapy was being held back, and he developed another sternal mass, prompting a fluorodeoxyglucose-positron emission tomography–computed tomography (PET/CT) scan to evaluate for relapse of myeloma. The scan revealed an enlarged, diffusely hypermetabolic right testicle. Believing the symptoms were related to the myeloma and not orchitis, the clinicians advised a radical orchiectomy.
A biopsy after the surgery showed tumor cells consistent with testicular plasmacytoma.
While rare, testicular plasmacytoma is commonly associated with MM, especially in the later stages, when cancer cells are more aggressive and not relying on bone marrow for survival, the clinicians say. Unlike myeloma, which typically spreads via blood to bone sites, testicular plasmacytoma may spread via lymphatic channels to the regional lymph nodes and subsequently to distant sites, the clinicians add, similarly to lymphoma or germ cell tumor.
It is hard to diagnose, though. The clinicians say the patient’s case illustrates the challenges. Imaging studies such as ultrasound and CT scans are not specific. And although FDG-PET/CT imaging is a standard staging tool for myeloma and helpful in identifying plasmacytoma when evidenced as intramedullary or extramedullary hypermetabolic lesions, hypermetabolic lesions are not always malignant, they note. FDG-PET/CT can’t differentiate between orchitis and testicular plasmacytoma. Biopsy remains the diagnostic gold standard.
Schiavo C, Mann SA, Mer J, Suvannasankha A. BMJ Case Rep. 2018;pii:bcr-2017-222046.