CASE PRESENTATION: An 82-year-old man with
autoimmune pancreatitis under treatment with oral
corticosteroids was found to have peripancreatic
lymphadenopathy on computed tomography. Subsequent positron emission tomography revealed abnormal uptake (maximal value 3.6) by a thymic mass as well as the peripancreatic lymph nodes. Exacerbation of
IgG4-RD was suspected, and we increased the oral
steroid dosage. As a result, the peripancreatic lymph nodes, and the anterior mediastinal mass, decreased in size. The thymic mass was suspected to be an encapsulated
thymoma because of its lobulated shape, degree of fluorodeoxyglucose accumulation, and response to
steroids, and the patient was referred to our department. The serum anti-
acetylcholine receptor antibody test was negative. A thoracoscopic
tumor resection was performed as diagnostic
therapy. Histopathological analysis revealed dense lymphoplasmacytic infiltration with sclerotic stroma within the
tumor. Immunohistochemical analysis revealed abundant IgG4-positive plasma cell infiltrates and over 50%
IgG4/
IgG-positive plasma cells. We did not see either
keratin-positive thymocytes or
terminal deoxynucleotidyl transferase-positive lymphocytes. Furthermore, deviation in the kappa chain and lambda chain-positive plasma cells was not noted. Accordingly,
IgG4-related sclerosing disease was diagnosed.
CONCLUSIONS: IgG4-related sclerosing masses in the anterior mediastinum are very rare, and the effect of
tumor resection on prognosis remains unclear.
IgG4-RD had potentially been categorized as
Castleman's disease.