Extramedullary progression despite a good response in the bone marrow in patients treated with thalidomide for multiple myeloma

We report two patients who were treated with thalidomide for resistant mult iple myeloma (MM) and developed extramedullary plasmacytomas despite a good response in the bone marrow, The first patient had progressive disease 18 months post autologous peripheral stem cell transplant. Two and a half mont hs after the initiation of thalidomide therapy extensive new plasmacytomas of the skin and nasal mucosa appeared while the medullary response continue d. The second patient was treated with thalidomide for resistant MM. Despit e a medullary response he developed neurological signs compatible with cran ial nerve involvement and an MRI study was suggestive of a plasmacytoma inv olving the sellar region. We assume that a change in the expression of some adhesion molecules on the myeloma and/or the stromal cells is responsible for this phenomenon. Treat ing Physicians should be aware of this phenomenon in MM patients receiving thalidomide.