Extramedullary Plasmacytoma on Unilateral Upper Eyelid in a Shih-Tzu Dog

Abstract

A 9-year-old spayed female Shih-Tzu was presented with a mass on the upper eyelid of the right eye (OD). The eyelid mass continued to enlarge along the eyelid margin and the eyelid skin. Throughout the follow-up examinations, the mass did not affect the palpebral conjunctiva OD. Until 9 months since the mass was first identified, the dog did not show any clinical signs related to the mass. However, after 11 months, the owner complained of the dog's discomfort on OD and decided on surgical excision of the mass. There were no abnormalities in the complete blood count and serum chemistry profiles. The pentagonal resection was performed to completely remove the mass in the eyelid. There were no suspicious findings of metastasis on whole-body computed tomography scan immediately before the surgery. On histopathology and immunohistochemistry for multiple myeloma oncogene-1, the eyelid mass was diagnosed as extramedullary plasmacytoma (EMP). Surgical margin of the mass was clearly cut. No recurrence was observed during the 5-month follow-up. EMPs on the eyelid have rarely been reported in dogs. Although EMP is a benign tumor, the mass showed invasive growth and grew toward the skin rather than the palpebral conjunctiva. No recurrence occurred when surgically removed with clean margins.