Emergence of cutaneous Rosai–Dorfman disease during immunosuppressive treatment of follicular B-cell lymphoma: A case report

BACKGROUND: Sinus histiocytosis with massive lymphadenopathy, also known as Rosai–Dorfman disease, is a rare proliferation of non-Langerhans histiocytes. Cutaneous Rosai–Dorfman disease is a rare subtype of Rosai–Dorfman disease limited to the skin with variable clinical presentation. CASE SUMMARY: A 59-year-old female with a history of osteoarthritis, hypothyroidism, and follicular B-cell lymphoma presented with pruritic, erythematous, dome-shaped papules that developed while on chemotherapy treatment. During cutaneous disease progression, the patient was further diagnosed with myelodysplastic syndrome. Histology review revealed patchy staining for S100 in the CD68+ histiocytes within the dermis with no enlarged histiocytes or emperipolesis. Given the absence of other findings, this was interpreted as cutaneous Rosai–Dorfman disease. CONCLUSION: There is still little known about the aetiology and pathogenesis of cutaneous Rosai–Dorfman disease. Non-specific immunohistochemistry in the midst of lymphoma, immunosuppressive treatments, and myelodysplastic syndrome produced a blurred diagnostic picture and delayed appropriate treatment, highlighting the diagnostic challenges of cutaneous Rosai–Dorfman disease.