Castleman's disease with numerous mantle zone lymphocytes with clear cytoplasm involving the skin: case report.

Castleman's disease (CD) is an unusual lymphoid hyperplasia occurring in the mediastinal lymph nodes and, less frequently, in the neck lymph nodes. CD is classified clinically into a unicentric and a multicentric type, whereas three histomorphological variants are recognized: the hyaline vascular type, the intermediate type and the plasma cell type. We report the clinical and pathological features of a 54-year-old female suffering with multiple sclerosis and developing a lymph node hyaline-vascular type CD relapsing in the skin after 24 months. Histological features showed a nodular dermatitis with atrophic germinal centers and an 'onion skin' rimming of lymphocytes in the mantle zone with numerous mantle zone lymphocytes with clear cytoplasm, with a CD20+, CD79a+, IgM+, IgG-, IgA-, CD5-, CD10-, CD43-, CD45RO-, bcl-2+ and bcl-6- phenotype with polytypic nature supporting the diagnosis of lymphoid variant of hyaline-vascular CD. This case shows that skin CD recapitulates all the histological variants of lymph node CD. Considering the many similarities between the present case and the primary cutaneous marginal zone lymphoma, it is important to bear in mind this atypical lymphoproliferative disorder in order to avoid overdiagnosis and overtreatment.