Rosai-Dorfman Disease (RDD) is a rare disease of histiocyte proliferation. It predominantly affects children and young adults, with a slight male preponderance. , Though the disease has the capacity to simulate a malignant process both clinically and pathologically, it has a benign clinical course.
A 25-year-old male presented with bilateral multiple cervical and submandibular swellings associated with fever since the past 5-6 months.
On examination, bilateral cervical and submandibular swellings of sizes ranging from 1 × 0.5 cm to 5 × 3 cm were found [Figure 1] and [Figure 2]. They were firm in consistency, nontender, and freely mobile. Peripheral smear examination was within normal limits. Fine-needle aspiration cytology (FNAC) revealed plenty of mature and transforming lymphocytes, plasma cells, and histiocytes showing emperipolesis (intact lymphocytes in the cytoplasm) [Figure 3] and [Figure 4].
Differential diagnoses include Langerhans cell histiocytosis (LCH), reactive lymph node hyperplasia with sinus histiocytosis (RLHSH), and hemophagocytic syndrome [Table 1].
Rosai-Dorfman disease (RDD) is a rare, benign, idiopathic, proliferative disease of phagocytic histiocytes. The etiology and pathogenesis of this disorder are unknown but are thought to represent a reactive histiocytic process to an infective agent rather than a neoplastic or other primary condition. 
The etiological agent is thought to be stimulation of monocyte/macrophage via macrophage colony-stimulating factor (M-CSF). 
The most common presentation of RDD is massive painless bilateral lymphadenopathy with fever, as in our case, and the most commonly involved site is a cervical lymph node. Extranodal involvement occurs in 30-40% of cases, most often in the head and neck. 
Immunohistochemistry results were: Cluster designation 68 (CD68) + ve, S100 +ve, and CD 1a -ve.  Cytodiagnosis is an important tool in RDD, as in our case.
Other associated conditions are malignant lymphoma, non-Hodgkin lymphoma, myeloma, melanoma, papillary carcinoma of thyroid, and immature teratoma of ovary. 
Mostly, the lymph nodes regress by themselves; however, some patients may require surgical debulking, and, rarely, radiotherapy and chemotherapy. 
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Read associated Letter to the Editor: Rosai-Dorfman disease: A case report with this article
[Figure 1], [Figure 2], [Figure 3], [Figure 4]