Castleman disease-type histopathological patterns of lymph nodes in patients with plasma cell neoplasia and POEMS syndrome.

Plasma cell neoplasia and POEMS syndrome patients may present Castleman disease (CD)-type features in lymph nodes. Our aim was to better characterize the histopathological patterns found in plasma cell neoplasia associated CD and to improve the detection of clonal plasma cell populations in the lymph node biopsies of these patients. Lymph node and bone marrow samples from six cases with plasma cell neoplasia associated CD, including POEMS syndrome and multiple myeloma were analyzed. A complete analysis including morphology, IHC and PCR-based clonality detection in the lymph node biopsies and morphology; IHC and FCM in the bone marrow biopsies was done. Correlation with clinical and laboratory features was performed. Both plasma cell rich and hyper vascular Castleman disease like histopathological features were found. In two out of six cases, sheets of plasma cells with light chain and isotype restriction were identified in the lymph nodes. B cell clonality analysis provided evidence of clonal populations in 5 out of 6 cases, increasing the sensitivity for the detection in cases without morphologically identifiable monotypic plasma cells. None of the twelve control cases with iMCD and HHV-8 positive CD showed clonal populations. In conclusion, the combination of morphology, complete immunophenotyping and B cell clonality analysis in the lymph node biopsy may provide evidence of clonal populations in up to 83 % of cases with plasma cell neoplasia/POEMS syndrome associated Castleman disease. Clinical work-up for the confirmation of plasma cell dyscrasia is advisable in such cases.