A reappraisal of sclerosing nodular and/or polypoid lesions of the gastrointestinal tract rich in IgG4-positive plasma cells.

Very few IgG4-related lesions in the tubular GIT are associated with disease at other sites and/or elevated serum IgG4 levels. The majority may represent a lesion in the spectrum of IgG4-related disease. The use of the term 'IgG4-positive nodule or polyp with probable histological features of IgG4-related disease' is advocated for nodular and/or polypoid lesions in the GIT with ≥10 IgG4-positive plasma cells in a high-power field and an IgG/IgG4 ratio of >0.4.