Ocular adnexal plasmacytoma presenting as a lesion of the plica semilunaris and caruncle in a 21-year-old male

Purpose Solitary extramedullary plasmacytoma (SEMP) makes up 2-5% of plasma cell dyscrasias and is defined as a plasma cell neoplasm in the absence of systemic multiple myeloma or other dyscrasia. A rare subset of SEMP is plasmacytoma located in the ocular adnexa, most commonly in the conjunctiva and orbital soft tissues. We present and discuss the case of an isolated mass of the caruncle and plica semilunaris in an otherwise healthy 21-year-old male. Observations A 21-year-old male with no past medical or ocular history presented with an enlarging, irritating mass in the left medial canthus. He had 20/15 visual acuity bilaterally and no deficits in extraocular motility. Magnetic resonance imaging revealed a T2-hyperintense, well-circumscribed lesion with no infiltration into the sinuses or other tissues. After excision, histopathological analysis confirmed plasmacytoma. The patient underwent a systemic workup for multiple myeloma, including bone marrow biopsy and serum immunofixation electrophoresis, that was unremarkable. After confirmation of no other sites of involvement, a diagnosis of ocular adnexal plasmacytoma was made and the patient underwent localized radiation. Conclusions and importance While ocular adnexal plasmacytoma has been reviewed in previous case studies, it is rare to identify this neoplasm in a healthy young adult. Biopsy is indicated to establish the diagnosis and guide treatment. No clinical trials exist on the treatment of ocular adnexal plasmacytoma; previous reports have demonstrated that cases respond well to localized radiation therapy or, if fully excisable, excision alone with close monitoring for recurrence. While ocular adnexal plasmacytoma has a lower risk for progression to multiple myeloma than bone marrow-derived plasmacytomas, patients should be monitored regularly after treatment by their ophthalmologist, primary care physician, or oncologist.