Rosai-Dorfman disease with features of IgG4-related disease in the breast: Cases report and literature review.

BACKGROUND A proportion of cases of Rosai-Dorfman disease exhibit some histological features consistent with IgG4-related disease (IgG4RD). Several investigators have discussed whether Rosai-Dorfman disease belongs to the spectrum of IgG4RD or is concurrent with it by coincidence. OBJECTIVE To elucidate the relationship between the two diseases, we report key features, including IgG4 and amyloid levels, of four cases of Rosai-Dorfman disease in the breast. METHODS The histological features of the four cases were analyzed and the numbers of IgG4+ plasma cells and IgG4/IgG ratios were evaluated. Serum IgG4 concentrations were also measured in two recent cases. A literature review was also performed. RESULTS Two cases (case 1 and 2) showed features of IgG4RD, including lymphoid follicle formation with regressive changes, obliterative phlebitis, increased number of IgG4+ plasma cells, and increased IgG4/IgG ratio; one of the two had an elevated serum IgG4 level. Amyloidosis was detected in these cases, with amyloid in the stroma and the vessel walls of the lesion. The other two cases (case 3 and 4) only had mild increases in the numbers of IgG4+ plasma cells, while amyloid was deposited in the stroma only. CONCLUSIONS A subset of Rosai-Dorfman disease may overlap with IgG4RD in the breast. When Rosai-Dorfman disease has features of IgG4RD, amyloidosis could be induced in the lesion.