Panniculitis as a unique manifestation of Rosai-Dorfman disease

A 33-year-old woman was admitted due to an 8-month history of multiple solitary subcutaneous masses on bilateral thighs, lower abdomen and waist. At first, she developed a small painless subcutaneous nodule on the right thigh and the lesion grew larger with time. One month later similar lesions developed on the left thigh, lower abdomen and waist. An excisional biopsy performed in an outside facility was interpreted as lupus panniculitis, and the patient was treated with hydroxychloroquine 200 mg twice a day for 2 months without any improvement. Because of the recalcitrant disease course, the diagnosis of lupus panniculitis was questioned, and the patient was referred to our hospital for another biopsy.
Physical examination revealed that firm non-tender subcutaneous masses were present on the bilateral thighs, lower abdomen and waist, ranging from 2 × 3 cm to 6 × 7 cm in diameter. The surface colour was dark red to brown. Increased hair growth was noted overlying the lesion (Figure 1 A). Previous biopsy scar was seen on the right thigh without recurrent lesions in the vicinity (Figure 1 B). There was no palpable lymphadenopathy or hepatosplenomegaly.
Her laboratory analysis disclosed the following values: antinuclear antibody (ANA) was positive with a titre of 1 : 320, while ds-DNA and the other autoimmune markers were negative. Serum protein electrophoresis levels were normal, and erythrocyte sedimentation rate was 15 mm/h. Results of the blood count, urine and biochemical profile were within normal limits. Other studies including rapid plasma regain (RPR), treponema pallidum particle agglutination assay (TPPA), human immunodeficiency virus (HIV), hepatitis B virus (HBV) and antibody against cytomegalovirus were all negative. Imaging studies including X-ray, computed tomographic scan and echocardiography were normal.
Histology of the representative lesion revealed normal epidermis, dermis and sheets of histiocytes with a pale pink cytoplasm surrounded by dense infiltrate of lymphocytes and plasma cells in the fat lobules. The large histiocytic cells had indistinct borders, abundant pale pink cytoplasm and large vesicular nuclei (Figure 2 A–C). The stain for S-100 protein highlighted these histiocytes and emperipolesis (Figure 2 D). Staining for CD68 was also positive but CD1a was negative. Direct immunofluorescence was negative. On the basis of the histiocytic infiltrate with emperipolesis and immunohistochemical staining results,...


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