Double CD38/CD138 negative multiple myeloma.

The standard diagnosis of multiple myeloma by flow cytometry is based on selection of population of CD38/CD138 positives cells. As the result treatment with proteasome inhibitors, CD138 may be underexpressed on atypical plasma cells. Thus, in order to improve this strategy, recently new CD138-independent method, based on CD38 positivity of plasma cells was developed. We present an unusual case of CD138 negative multiple myeloma which had become double CD138/CD38 negative after treatment with daratumumab by which we would like to illustrate potential pitfalls of both strategies.