Non-secretory myeloma is a myeloma subtype whose diagnosis, until a few years ago, was established by demonstration of monoclonal plasma cells in the bone marrow and by negative results on serum and urine electrophoresis and immunofixation studies. However, this type of myeloma could be misdiagnosed if the workup does not include an accurate study of serum free light chain test since some of the patients diagnosed as non-secretory could be light chain only with small amounts monoclonal proteinuria. Due to this limit in classification, all the information available today, generally coming from retrospective studies including patients studied in a complete and incomplete fashion, could be misleading. A new definition is thus needed to distinguish between the true non-secretory, with a possible better prognosis, and the other forms of oligosecretory myeloma with a prognosis more similar to the secretory form of myeloma. With all the data of the literature, the availability of laboratory and radiological tools, times are mature to depict a new definition of non-secretory myeloma which deserves, a peculiar work up and different response evaluation and, maybe, a different therapeutic approach.
Keywords: Non-secretory myeloma; Free light chain; Myeloma subtype.