Purpose: Clinical phenotypes in Immunoglobulin G4-related disease (IgG4-RD) according to the affected organs affected have different risks of malignancies. We attempt to determine the association of malignances with IgG4-related ophthalmic disease (IgG4-ROD).Design: Retrospective cohort study. Methods: Review of medical records, orbital images and histopathology reports in a territory-wide cohort of patients ful lling the "probable" or "de nite" comprehensive diagnostic criteria of IgG4-RD from 2005-2019.Findings: Among 122 patients who had biopsies taken from adnexal lesions including lacrimal glands (n=108), orbital mass (n=30), in ltrated orbital fat (n=10), conjunctiva (n=2) or extraocular muscles (n=3), 16 (13%) developed malignancies over 73±48months' follow-up. There were 9 cases of ocular adnexal lymphoma (OAL) and 7 extra-orbital malignancies. Compared with the general population, the incidence of OAL was signi cantly higher (standardized incidence ratios, SIRs=10.0, 95%CI=4.5-17.6) while that of extraorbital malignancy was similar. The SIR was highest within the rst year (SIR=46.7, 95%CI=18.5-87.6) when 7 OAL were concomitantly diagnosed. Patients who developed OAL or extra-orbital malignancies were older than other patients when diagnosed of IgG4-ROD (64.9±7.1, 68.3±8.5 versus 55.2±15.0 years, p<0.05). Asymmetric lacrimal gland enlargement (78% versus 13%), lack of frontal (0% versus 12%) or infraorbital nerve enlargement (0% versus 36%)were associated with OAL (all p<0.05). Pre-treatment serum IgG4 level or pattern of extraorbital involvement was similar among patients with or without malignancies. Conclusion:In this biopsy-proven IgG4-ROD cohort, 7% developed OAL which was 10 times higher than the general population. Patients with asymmetric lacrimal gland enlargement or without trigeminal nerves involvement radiologically were associated with OAL.