Numerous IgG4-positive plasma cells are ubiquitous in diverse localised non-specific chronic inflammatory conditions and need to be distinguished from IgG4-related systemic disorders

IgG4-related systemic fibrosclerosis is a recently defined disorder characterised by a diffuse or tumefactive inflammatory reaction rich in IgG4-positive plasma cells associated with sclerosis and obliterative phlebitis. Although characteristic histopathological features are essential for the diagnosis of these disorders, to date there exists no consensus regarding the cut-off values used to define a 'significant IgG4-positive plasma cell...