IgG4-related sclerosing disease: an emerging entity frequently misdiagnosed.

IgG4-related sclerosing disease, a multiorgan system disease that has been identified in the last 10 years, is a fibroinflammatory condition with a marked propensity to manifest itself as mass forming lesions characterized by three main histological features (sclerosis, obliterative phlebitis and lymphoplasmacytic infiltrate) and by the presence of abundant IgG4+ plasma cells, frequent elevation of serum IgG4 and a dramatic initial response to steroid therapy. The aim of this mini-review is to increase the capacity to identify the characteristic features of IgG4-related sclerosing disease in specific organs and in two newly proposed entities (urethral caruncle and paratesticular fibrous pseudotumor) using biopsy specimens and methods of counting IgG4. In addition we examine the relationship between IgG4-related sclerosing disease and malignancy. In fact, an increased ability to recognize the characteristic features of IgG4-related sclerosing disease would play an extremely important role in avoiding unnecessary surgery in favor of initiating corticosteroid therapy.