Inflammatory Fibroid Polyps of Gastrointestinal Tract Rarely Show Increased IgG4 Expression

Inflammatory Fibroid Polyp (IFP) of gastrointestinal tract is characterized by concentric perivascular fibrosis and a mixed inflammatory infiltrate rich in eosinophils and also few plasma cells. IgG4-related sclerosing diseases (IgG4-RSD) are a heterogenous group of disorders described in many organs, characterized by a significant increased of IgG4+ plasma cells in a context of storiform fibrosis, obliterative vasculitis and mixed inflammatory infiltrate containing eosinophils. The histological similarities between IFP and IgG4-RSD prompted the present study in the attempt to find a possible link between IgG4 over-expression and IFP. The expression of IgG4 and IgG was evaluated in a series of 23 cases of IFP belonging to 23 patients. All cases were reviewed by two pathologists and the histological diagnosis confirmed. Immunohistochemistry for antibodies anti-IgG, anti-IgG4, and anti-IgA was performed on all cases and the results were evaluated by two observers. One case of IFP out of 23 (4.3%) fulfilled the IgG4-RSD histological criteria. The case did not differ histologically from the others. The patient did not present either a raised serological level of IgG4, nor other sign of IgG4-RSD. IgG4 increased expression can be rarely observed in IFP. Steroid therapy in cases of IFP with abundant IgG4+ plasma cells, especially in patients with multiple tumors, could be considered as an alternative to surgical treatment.