Castleman's disease of the leptomeninges--immunohistochemical findings in 2 cases.

Objective: Castleman's disease is an uncommon benign lymphoproliferative disorder that arises in lymph nodes. Few cases of Castleman's disease affecting the central nervous system have been described. Case history: We report 2 new cases of Castleman's disease confined solely to the leptomeninges. The patients were referred to neurosurgery with presumptive clinical diagnosis of meningiomas. Histological investigation of the operative specimens taken from the abnormal leptomeninges revealed nodular lymphoid areas with multiple germinal centers surrounded by concentrically layered proliferations of small lymphocytes. Histologically, these 2 cases fulfilled the classification criteria for the mixed and for the hyaline-vascular type of Castleman's disease. The immunohistochemical analysis revealed a polyclonal B cell proliferation in the lesions with perifollicular T cell proliferation with the T helper cell predominance. Conclusions: The authors conclude that Castleman's disease involving the leptomeninges have a similar immunological pattern reported for the disease in extracranial locations and that, though being rare, Castleman's disease should be considered as a differential diagnosis when dealing with mass lesions of leptomeninges.