A 65-year-old woman presented with a flank mass. A biopsy was performed and the resultant specimen is illustrated below.
The mass consists of a cellular fibroinflammatory proliferation with prominent histiocytes, plasma cells and lymphocytes. The histiocytic component predominates and consists of markedly enlarged cells with eosinophilic to foamy cytoplasm and easily identified intracytoplasmic lymphocytes and plasma cells. Immunohistochemical studies showed that the histiocytic cells were positive for S100 protein and negative for CD1a.
What is your diagnosis?
This is an extremely nice example of sinus histiocytosis with massive lymphadenopathy (SHML), also known as Rosai-Dorfman disease. Hint: To get a disease named after you, give it is helpful to give it a very long name originally! The histiocytic cells demonstrate florid emperipolesis, a classic finding in this lesion. As the term, sinus histiocytosis with massive lymphadenopathy implies, this process was first described in and most frequently involves lymph nodes. However, virtually any anatomic site may be involved with skin, sinonasal region, soft tissues and bone being common extranodal locations. SHML occurs over a wide age range from newborns to the elderly.
Although the histiocytic cells of SHML share S100 protein positivity with Langerhans cell proliferations, they are not considered to belong to the family of Langerhans or dendritic cells and their lack of reaction for CD1a and Langerin are of value in making this distinction diagnostically. SHML is typically indolent and self limited, although prognosis does correlate with the number of involved sites. Patients with persistent or progressive disease have been variably treated with surgery, radiation, and chemotherapy. Patients with widespread disease often have an associated immune dysfunction. Although SHML is occasionally a cause of death, I am not aware of any cases undergoing malignant transformation.