Testicular plasmacytoma: A comprehensive case series and review.

Abstract

e19565 Background: Testicular plasmacytoma (TP) is a rare manifestation of plasma cell neoplasms, occurring alone or with multiple myeloma (MM). Diagnosis is challenging due to nonspecific presentation, and literature is limited to small case reports. We aimed to characterize TP’s clinical presentation, management, and outcomes at a large tertiary center. Methods: We retrospectively reviewed over 7,000 PCN patients treated between 2007 and 2025. Patients with TP confirmed by imaging, biopsy, or orchiectomy and complete data were included. A concurrent literature review was performed. Demographics, labs, pathology, imaging, treatments, and survival outcomes were analyzed. Results: A literature review identified 34 cases and 5 clinical patterns of TP based on disease timing and progression. Our case series included 17 TP patients, the largest single-institution cohort to date. Eighty-eight percent (patterns 2, 3, and 5) had underlying MM, with type 4 most common. Median age was 57 years, and IgG was the predominant isotype. Over half had osseous plasmacytomas on PET/CT, although most lacked diffuse bone marrow involvement at diagnosis. Median overall survival was ~4 years, with one patient surviving beyond 18 years. Conclusions: TP is extremely rare and usually represents secondary involvement in active or relapsed MM rather than de novo disease. No cases of primary TP were observed, highlighting the importance of long-term follow-up to detect progression to systemic disease. Radical inguinal orchiectomy remains central for diagnosis and local control, with radiation used selectively. Systemic therapy follows standard myeloma regimens, and prognosis is primarily determined by underlying MM biology. Literature review: Patient characteristics and five clinical patterns. Patient Cohort No. of patients Age, years Presentation M-Protein MM Status Treatment De novo solitary TP (Pattern 1) 11 72 (34–86) Painless scrotal swelling; unilateral (9); bilateral metachronous (2) Absent No prior MM or extramedullary PCN Orchiectomy ± XRT (1) or CT (2) TP as the first manifestation of MM (Pattern 2) 3 69 (62–73) Painless scrotal swelling without systemic symptoms Absent (2); IgA-λ light chain restricted (1) New MM diagnosis Orchiectomy + CT ± XRT (1) TP during active multiple myeloma (Pattern 3) 3 47 (43-72) Painless scrotal swelling λ light chain restricted (3) Active, relapsed or residual Orchiectomy ± CT (2) TP with other extramedullary PCN (Pattern 4) 7 57 (38–77) Painless scrotal swelling Absent (2), IgA (1), IgG (1), or λ light chain restricted (3) Active (3), relapsed (1) or no disease (3) Orchiectomy ± CT (5) ± ASCT (3) TP as MM relapse (Pattern 5) 10 54 (39–81) Painless or painful scrotal swelling IgA (5) or IgG (2), λ light chain restricted (7) Relapsed MM Orchiectomy, CT ± XRT (2) ± ASCT (1) LN: lymph nodes, PCN: plasma cell neoplasm; MM: Multiple Myeloma; CT: chemotherapy; XRT: radiation; ASCT: autologous stem cell transplant.