Immunoglobulin G4-related lymphadenopathy with inflammatory pseudotumor-like features.

Immunoglobulin (Ig) G4-related disease has been recently described. This disease affects various organs, including lymph nodes. We describe the case of a 52-year-old Japanese man with IgG4-related lymphadenopathy with inflammatory pseudotumor (IPT)-like features. Five years ago, the patient noticed a painless mass in the mandible but did not consult a doctor. Recently, he noted that the mass had increased in size and consulted an oral surgeon in the hospital. Excisional biopsy was performed for diagnosis. Histopathological examination revealed that most of the enlarged lymph node was occupied by the hyalinized tissue. A few residual lymphoid follicles with hyperplastic germinal centers and infiltration of plasma cells and eosinophils were observed. Most of the plasma cells expressed IgG4, and the ratio of IgG4-positive cells to IgG-positive cells was 57.1%. These findings were consistent with IgG4-related lymphadenopathy. In conclusion, pathologists should consider IgG4-related lymphadenopathy when diagnosing a lesion with IPT-like features.