Primary extramedullary plasmacytoma: similarities with and differences from multiple myeloma revealed by interphase cytogenetics

Primary extramedullary plasmacytoma is an indolent neoplasm that infrequently converts to multiple myeloma. Since cytogenetic data on extramedullary plasmacytoma are lacking, we studied 38 cases of this type of neoplasm by fluorescence in situ hybridization. Fourteen cases (37%) contained IGH breaks, including six with a t(4;14) translocation. No translocations t(11;14), t(14;16), t(8;14), nor breaks involving MALT1, BCL6 or FOXPI were found. Loss of 13q (40%), as well as chromosomal gains (82%) were common.There was no correlation between chromosomal alterations and clinical features or local relapse. Cytogenetically, extramedullary plasmacytoma and multiple mueloma are closely related. However, the distribution of IGH translocation partners, with the notable absence of t(11;14), is different.