Immunohistochemical and ultrastructural study of unusual IgM lambda lymphoplasmacytic tumor of the lacrimal gland

A 72-year-old man developed a slowly enlarging mass involving the left lacrimal gland. Excisional biopsy disclosed a lymphoplasmacytoid tumor which was found by immunohistochemistry techniques to be a monoclonal proliferation, expressing cytoplasmic IgM lambda. However, serum protein immunoelectrophoresis disclosed a monoclonal spike in the gamma-globulin region with IgG lambda. The patient was still systemically well with no evidence of lymphoma almost ten years after the initial recognition of the lacrimal gland mass. This unusual case demonstrated the difficulty of classifying orbital lymphoid tumors and the problems of accurately predicting the clinical course and prognosis in affected patients.