Plasma Cell Granuloma: An Entity within the Spectrum of IgG4-Related Disease

Plasma cell granuloma (PCG) is a relatively rare, mass-forming lesion comprised of polyclonal plasma cells set in a background of storiform fibrosis and spindle cell proliferation. While uncommon, this lesion may occur within any site and should be included in the list of differential diagnoses for plasma cell neoplasms. As this entity can be mistaken for a plasma cell neoplasm, surgical pathologists should consider ancillary studies to assess clonality of plasma cell proliferations, especially during intraoperative consultation.Although the etiology of these lesions is unclear, recent literature and immunohistochemical stains performed on our own cases suggest that PCG falls within the spectrum of IgG4 related diseases, which would have significant clinical significance impacting treatment and the potential for associated disease at distant body sites. We present two cases of head and neck PCG encountered at a tertiary academic medical center with immunohistochemical staining demonstrating increased IgG4-secreting plasma cells.