Solitary Extramedullary Plasmacytoma of the Lacrimal Sac with Associated Crystal-Storing Histiocytosis

Purpose: To report a rare case of crystal-storing histiocytosis associated with solitary extramedullary plasmacytoma of the lacrimal sac and to review literature on the 2 entities to summarize important diagnostic, management, and prognostic considerations. Methods: A case report of the ophthalmologic presentation, pathology workup, and oncologic management is presented. Literature search with focus on lesions occurring in ophthalmic sites and management guidelines from expert panels and working groups. Results: Crystal-storing histiocytosis associated with solitary extramedullary plasmacytoma arose within the lacrimal sac of a previously healthy middle-aged woman and presented as a painless nodule with epiphora. The biopsy tissue showed sheets of crystal-filled histiocytes, interspersed with monoclonal plasma cells and rarely demonstrated plasma cell phagocytosis. Imaging and laboratory studies confirmed the localized nature. Conclusions: Crystal-storing histiocytosis is an uncommon entity in which crystals, most commonly arising from altered immunoglobulins, aggregate within histiocytes and form symptomatic mass lesions. It has been reported in ophthalmic regions in patients with a concurrent lymphoproliferative or plasma cell disorder and can rarely predate a malignancy. The current case is notable because crystal-storing histiocytosis occurs with a localized process, solitary extramedullary plasmacytoma, and presents in an unusual site, the lacrimal sac. Tissue biopsy with multimodal pathological evaluation is necessary to make the diagnosis. Ophthalmologists should recognize that crystal-storing histiocytosis is commonly associated with a hematologic malignancy and, when appropriate, refer the patient for oncologic management. Surveillance may be indicated in cases with no established etiology. Solitary extramedullary plasmacytoma should also be monitored, as a proportion of cases progress to multiple myeloma.