Diagnosis of IgG4-related ophthalmic disease (IgG4-ROD) rests on the correlation of clinical features, serological testing and histopathology, using internationally accepted diagnostic criteria for objective interpretation; however, several mimickers of IgG4-RD overlap in clinical presentation and histopathology. We assess histopathological features in a series of presumptive IgG4-ROD cases, with emphasis on histopathological mimics and comparison of three IgG4-ROD diagnostic/classification criteria (organ-specific (OS), revised comprehensive diagnostic (RCD) and American College of Rheumatology/European Alliance of Associations for Rheumatology (ACR/EULAR) criteria).