The patient is a 64-year-old male with a history of non-alcoholic steatohepatitis with cirrhosis.  A PET-CT performed upon evaluation for a liver transplant showed multistational lymphadenopathy, splenomegaly, numerous scattered osseous sclerotic lesions, and diffuse hypermetabolism of the axial and appendicular marrow compartment.  The excisional supraclavicular lymph node biopsy as well as a bone marrow biopsy were performed for further evaluation. 

The lymph node demonstrates a partially preserved architecture and is moderately enlarged by paracortical aggregates of atypical spindled mast cells (positive for CD25, CD117, CD30, and are negative for CD2). In addition, multifocal aggregates of S100+ histiocytes, including histocytes with cytophagocytosis are seen, consistent with foci of Rosai-Dorfman disease. Plasma cells are increased.  They are polytypic by kappa and lambda immunohistochemistry (no evidence of a clonal population).  However, increased IgG4-positive plasma cells are identified throughout the paracortical regions; they are >50 cells/high power field in several foci and focally >40% of IgG positive cells are IgG4 positive. Increase in IgG4 may be seen in association with Rosai-Dorfman disease and a subset of Rosai-Dorfman disease may exhibit features of IgG4-related disease (Zhang et al.).    

The patient went on to have a bone marrow biopsy and next generation sequencing, which are discussed in an separete image set.  

Ref:

Zhang X, et al. A subset of Rosai-Dorfman disease exhibits features of IgG4-related disease. Am J Clin Pathol. 2013 May;139(5):622-32 doi: 10.1309/AJCPARC3Y Q0LIOA