Glucocorticoid-induced redistribution lymphocytosis in mantle cell lymphoma with hyaline vascular Castleman disease-like features.

We report a case of mantle cell lymphoma mimicking Castleman disease. A 76-year-old man presented with generalized lymphadenopathy, splenomegaly, anemia, polyclonal gammopathy, and pulmonary infiltrations. Lymph node biopsy revealed histological features of hyaline vascular Castleman disease. Treatment with prednisolone induced lymphocytosis with immunophenotypic and genetic features of mantle cell lymphoma. A detailed immunohistochemical study of the lymph node demonstrated a mantle cell lymphoma-mantle zone growth pattern. Glucocorticoid-induced distribution lymphocytosis has not been reported in mantle cell lymphoma. Careful observation of circulating lymphocytes during steroid treatment may enable diagnosis of the underlying occult lymphoma in a subset of patients exhibiting clinical manifestations of Castleman disease.