Large cell lymphoma of the orbit with microvillous projections ('porcupine lymphoma')

A 57-year-old man had a diffuse mass in the lacrimal gland area associated with extensive bony destruction. A malignant epithelial tumor of the lacrimal gland was suspected clinically, and a biopsy specimen disclosed an undifferentiated malignant neoplasm of uncertain origin. Ultrastructural studies, however, revealed features of a lymphoid tumor with myriad cytoplasmic microvillous projections. The patient has had no evidence of systemic lymphoma after more than three years of follow-up. To our knowledge, this is the first report of orbital involvement of a large cell lymphoma with microvillous projections ("porcupine lymphoma"). The role of electron microscopy in the differential diagnosis of this orbital tumor was important, since epithelial tumors of the lacrimal gland are best managed by surgical excision, whereas lymphoid tumors usually respond satisfactorily to radiotherapy.