Joud H. Haidar

Loss of CD20 expression in relapsed lymphomas after rituximab therapy

Abstract: The response rate at relapse to rituximab in prior responders B‐cell non‐Hodgkins lymphoma (NHL) patients is below 50%. Loss of CD20 expression after rituximab therapy may explain this secondary resistance. However, the frequency of CD20 negative relapses cannot be assessed since most patients that relapsed after rituximab therapy have not been re‐biopsied. Here, we present two patients with CD20 positive low grade B‐cell NHL that lost the cell surface and cytoplasmic expression at relapse after rituximab therapy. Our findings suggest that confirmation of CD20 expression on the malignant B cells is required whenever rituximab therapy is considered.

Thiamine-responsive myelodysplasia

The triad of thiamine‐responsive anaemia, diabetes mellitus and deafness has been reported in 15 patients with macrocytic anaemia, sometimes associated with moderate thrombocytopenia. The bone marrow aspirate usually shows megaloblastic changes and ringed sideroblasts. However, tri‐lineage myelodysplasia has never been reported. We describe two patients who presented with diabetes, deafness and thiamine‐responsive pancytopenia. Bone marrow aspirate and biopsy were typical of tri‐lineage myelodysplasia. These findings suggest that thiamine may have a role in the regulation of haemopoiesis at the stem cell level. We propose the term ‘thiamine‐responsive myelodysplasia’ rather than that of thiamine‐responsive anaemia.

Serum Flt3 Ligand Variation as a Predictive Indicator of Hematopoietic Stem Cell Mobilization

Flt3 ligand (FL) is a good indicator of bone marrow (BM) cellularity, having a reciprocal relationship with white blood cell (WBC) count in aplastic anemia and chemotherapy-induced neutropenia. In this report, serum FL level was measured by enzyme-linked immunosorbent assay (ELISA), in 16 consecutive patients undergoing autologous peripheral stem cell transplantation, with an average of 12 selected levels for each patient based on major changes of WBC counts at different procedure stations. We found a significant increase of serum FL level at the WBC nadir after mobilization chemotherapy and a more dramatic increase at the WBC nadir post transplantation, consistent with a more profound BM aplasia after myeloablative chemotherapy as compared to high-dose cyclophosphamide used for mobilization. Hence, we reproduced the reciprocal relationship between serum FL and BM cellularity. A direct correlation between the increase of FL level after mobilization chemotherapy and the length of mobilization was also established, which may help physicians, at the individual patient level, to predict the time of stem cell collection. Finally, we showed a direct correlation between the peripheral CD34+ count at the time of stem cell collection and the peak FL level after transplantation, which can reflect BM stromal cell function. Our results suggest that variation of serum FL level may be used as predictive indicator of hematopoietic stem cell (HSC) mobilization.

Signet ring-like light chain myeloma with systemic spread.

Abstract: The morphological presentation of malignant plasma cells in multiple myeloma (MM) varies from mature to anaplastic plasma cells with only one reported case of signet ring variant. We describe here another case of signet ring‐like lambda light chain MM associated with extra‐skeletal spread to lymph nodes, spleen and liver. The clinical and pathological presentations were atypical with no evidence of bone‐lytic lesions or monoclonal component on protein electrophoresis, leading to a delay of several years in the diagnosis. Recognition of this morphological entity of MM may help in an early diagnosis of this rare variant.