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.