Submandibular lymph node. A: Several progressively transformed germinal centers (PTGC) are observed at a low magnification. B-C: Immunostaining for IgG (B) and IgG4 (C). Many plasma cell infiltrates are seen, and the IgG4+/IgG+ cell ratio is more than 40%, which is consistent with PTGC-type IgG4-related lymphadenopathy.
Fujii et al. Diagnostic Pathology 2014 9:41 doi:10.1186/1746-1596-9-41