We report two unusual cases of hyaline vascular type Castleman's disease showing a pale clear cuff of mantle zone lymphocytes presenting a marginal zone distribution pattern. These cells had medium-sized round or slightly indented nuclei and a moderate amount of clear cytoplasm. The histopathologic findings in our cases were similar to those of nodal marginal zone B-cell lymphoma. However, immunohistochemistry demonstrated that both the mantle zone lymphocytes and the pale cuff of the lymphoid cells were CD20+, CD79a+, sIgM+, sIgD+, CD5-, CD10-, CD43-, CD45RO-, Bcl-2+, Bcl-6- and cyclin D1-. The polytypic nature of these cells was demonstrated by immunohistochemistry and polymerase chain reaction. Reactive lymph node lesions only rarely show mantle cell hyperplasia with clear cytoplasm. This unusual mantle cell hyperplasia with clear cytoplasm associated with a hyaline vascular type of Castleman's disease should be differentiated from nodal marginal zone B-cell lymphoma, mantle cell lymphoma and follicular lymphoma. To avoid overdiagnosis and overtreatment, it is suggested that immunophenotypic and genotypic studies might be required, and furthermore careful attention should be paid to the morphologic examination.