Primary Plasma Cell Leukemia Presenting Mainly with Negative CD38 Expression at Diagnosis: A Case Report with Literature Review

The loss of CD38 expression has been described in multiple myeloma (MM) patients with relapsed/refractory disease and patients receiving CD38 monoclonal antibodies. However, the loss of CD38 at diagnosis is extremely rare with very few reports describing such finding in newly diagnosed MM patients. Only two detailed case reports described CD38-negative clonal plasma cells at diagnosis. However, none of these cases was primary plasma cell leukemia (PCL). We describe an elderly patient with primary PCL presenting mainly with a negative CD38 expression, which, to the best of our knowledge, has never been described. The patient did not do well and died within 3 months of diagnosis. The loss of CD38 expression at diagnosis could indicate more aggressive disease biology.