Rosai-Dorfman disease: A rare presentation as an isolated axillary lymphadenopathy, a case report and literature review.

Introduction: Rosai-Dorfman disease (RDD) is a rare histiocytic neoplasm. It most commonly presents with bilateral cervical lymphadenopathy. We report the fourth case in the literature of RDD presenting as isolated axillary lymphadenopathy.

Case Report: We report the case of a 55-year-old female patient who presented with right axillary lymphadenopathy that had persisted for 1 year, without other associated symptoms. Physical examination revealed an isolated right axillary lymphadenopathy. An excisional biopsy of the lymph node was performed, and histopathological findings were consistent with Rosai-Dorfman's disease. Regular follow-up was recommended.

Discussion: RDD is an uncommon histiocytic disorder. Initially identified in the 1960s as a benign, self-limited condition, RDD is now classified as a neoplastic disorder with causative mutations in the MAPK pathway. The classic presentation involves extensive, painless bilateral cervical lymphadenopathy. Isolated axillary lymph node involvement, as seen in our patient, is a rare presentation of nodal RDD with only three cases reported in the literature to date. Histologically, RDD is characterized by a prominent histiocytic infiltrate set against a background of inflammatory cells, primarily composed of lymphocytes and plasma cells. These histiocytes are typically hypochromatic, with abundant pale cytoplasm, and exhibit varying degrees of emperipolesis. In 2018, consensus guidelines for the management and evaluation of RDD were introduced.

Conclusion: Recent advances in genetic sequencing have reclassified RDD from a benign inflammatory disorder to a histiocytic neoplasm. Further research is needed to fully understand its implications for prognosis and treatment strategies.