Castleman's disease and sarcoidosis, a rare association resulting in a "mixed" response: a case report.

Introduction: Multicentric Castleman's disease is a rare lymphoproliferative disorder whose hallmark is atypical lymph node hyperplasia. Symptoms can include fever, splenomegaly, and abnormal blood cell counts. High levels of interleukin 6 (IL-6) are observed frequently in this disorder and are believed to drive the disease. Recently, therapies that target interleukin-6 or its receptor have been shown to be effective in Castleman's disease.

Case Presentation: We report the case of a 76-year-old Caucasian man with aggressive biopsy-proven Castleman's disease who experienced pulmonary and lymph node involvement, as well as fever and weight loss. He was treated with siltuximab, a chimeric anti-interleukin-6 antibody. After 5 months, fluorodeoxyglucose positron emission tomography computed tomography scans showed marked improvement in his lungs, but worsening mediastinal disease, consistent with a mixed response. Biopsy of the mediastinal disease revealed lymphoplasmacytic infiltrate with non-caseating, ill-defined granulomas and scarring consistent with sarcoidosis. Prednisone 50mg by mouth daily was started, which was tapered to 2.0-5.0mg daily. Siltuximab was continued. A subsequent fluorodeoxyglucose positron emission tomography computed tomography scan showed near-complete resolution of lung and mediastinal disease, now ongoing for 3.5+ years without serious adverse events.

Conclusions: Lymphomas have previously been reported to coexist with sarcoidosis, albeit rarely, but there has been only a single previous case of this type with Castleman's disease. Of importance, early recognition of the presence of sarcoidosis in our patient prevented discontinuation of siltuximab therapy due to "progression". Our experience may also have broader implications in that it suggests that etiology of "mixed responses" should be confirmed by performing biopsies on the progressive tumor.