To describe patients with periocular solitary extramedullary plasmacytoma (SEMP) and multiple myeloma (MM), together with an estimate of the risk of progression from SEMP to MM.
A retrospective case-note review for patients seen between 1978 and 2020, examining demographics, presentation, imaging, pathology, management, and outcome.
Twenty patients (10 male; 50%) presented at a mean age of 60.9 years, with an average symptom duration of 4.5 months. Ten (50%) patients had known systemic myeloma at ophthalmic presentation (the MM group) and, on average, they presented one decade earlier than those with occult MM discovered after orbital biopsy (p = 0.06); the majority (9/15; 60%) of patients with MM were female, whereas there was a male bias (4/5; 80%) with SEMP (p = 0.30). Most tumors (15/20; 75%) were within the anterior part of the orbit, especially superolaterally (16 patients; 80%), and the soft-tissue mass often appeared to “explode” from the frontal bone or greater wing of the sphenoid (16/20; 80%). Full treatment details were known for 19 patients: 6 (32%) had solely orbital radiotherapy, 4 (21%) chemotherapy, 6 (32%) combined chemoradiation, and 3 (16%) had combined chemoradiation with stem-cell transplant (Table 3). After an average follow up of 58 months, 1/5 (20%) patients with SEMP and 11/15 (73%) with MM had tumor-related death. The overall survival probability for all 20 patients with periocular plasmacytoma was 34% at 5 and 10 years, with MM patients having a worse outlook (27% 5-year, and 18% 10-year survival) compared with SEMP (53% survival at 5 and 10 years) (p = 0.18). None of the 5 patients with SEMP progressed to systemic MM over an average follow up of 9.1 years.
Although 50% patients with periocular plasmacytoma appear to have a SEMP at ophthalmic presentation, a half of these patients were found to have occult MM within 6 months of biopsy. Of those without systemic disease around the time of biopsy, none developed MM over an average follow up of more than 9 years.

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