CD138/syndecan-1: A useful immunohistochemical marker of normal and neoplastic plasma cells on routine trephine bone marrow biopsies

Detection of abnormal numbers and/or distribution of bone marrow (BM) plasm a cells (PCs) on trephine biopsies can be important in the differential dia gnosis of multiple myeloma (MM) and other PC disorders. A variety of immuno histochemical markers can potentially improve the specificity and sensitivi ty of PC detection on routine histological sections obtained from trephine BM biopsies, but most of them are not completely satisfactory. In this stud y, we investigated whether the antibody CD138/B-B4, which is an optimal mar ker for PC detection on BM aspirates by flow cytometry, can be used success fully for the identification of PCs also on formalin-fixed, decalcified bio psies. A series of samples including normal BM [12], MM [65], monoclonal ga mmopathies of undetermined significance [44], and B-cell lymphoma of variou s types [94], including B-cell precursor lymphoblastic leukemia [9], lympho plasmacytoid [17], immunoblastic [14], lymphocytic/CLL [23], hairy cell leu kemia [4], large B-cell [8], mantle-cell [3], marginal zone [6] and follicu lar [10] lymphomas, have been investigated for CD138 expression using a sen sitive immunohistochemical technique. Within the BM microenvironment, CD138 was characterized by excellent sensitivity and specificity. Virtually all normal and neoplastic PCs expressed clear-cut membrane CD138 immunostaining , whereas all other cell types did not. All cases of MM, including plasmabl astic and leukemic cases, showed strong immunoreactivity, Conversely, all B -cell lymphomas, including all cases characterized by secretive features, l ymphoplasmacytoid, and immunoblastic lymphomas, were completely negative. T hese results demonstrate that CD138 is a highly sensitive and specific mark er that is useful for the rapid and precise localization of normal and neop lastic PCs on routine BM sections. In addition, because of its clear-cut ce ll membrane localization, CD138 can be used successfully in double-marker i mmunostaining reactions to evaluate precisely nuclear prognostic markers su ch as Ki67 and p53 in MMs.