"In situ" mantle cell lymphoma associated with hyaline-vascular Castleman disease.

Mantle cell lymphoma (MCL) is a very rare non-Hodgkin B-cell lymphoma, with an aggressive clinical course and poor response to conventional therapy. Few cases of "in situ" MCL were reported in the last years. We present the case of a 31-year-old woman with a unique cervical lymphadenopathy. The morphologic findings are of hyaline-vascular Castleman disease (HV-CD). Immunohistochemical stain for cyclin D1 detects scattered cyclin D1+ cells within the mantle zones of few reactive-appearing lymphoid follicles, corresponding to the definition of "in situ" MCL. We also performed cyclin D1 in other 27 cases of CD (13 HV-CD and 14 plasma-cell CD) but the reported case was the only who associated "in situ" MCL. An adequate immunohistochemical panel, including a marker for cyclin D1, is required to differentiate this neoplasm from follicular hyperplasia. From our knowledge, this is the first reported case of "in situ" MCL associated with HV-CD.