Investigation and treatment
Upon investigation, the complete blood count (CBC) revealed a white blood cell (WBC) count of 45,000 cells/µL, with absolute lymphocyte count of 34,000 cells/µL(75%), neutrophil count of 6200 cells/µL, Hemoglobin 12.7 g/dL, platelet 123,000 cells/µL. Liver function tests, and renal function tests were normal, urinalysis was bland. The skeletal survey with x-ray skull, spine, pelvis, ribs and extremity was unremarkable.  Abdominal ultrasound revealed mild fatty liver otherwise no remarkable findings. The pathology report of Peripheral morphology showed 85% of blast cells having enlarged nucleus with condensed chromatin, inconspicuous nucleoli, and scant bluish cytoplasm (Figure 1). Bone marrow aspiration revealed particulate hyper cellular marrow flooded with blasts accounting for 80%. In conclusion the peripheral morphology and BMA were suggestive of acute leukemia in favor of acute lymphoblastic leukemia. Since the diagnosis of ALL was considered, BCR-ABL FISH study for BCR-ABL t(9:22) Philadelphia chromosome analysis was done and reported negative. With the morphologic diagnosis of acute lymphoblastic leukemia, the patient was started on dexamethasone for cytoreduction. After a few days of therapy, the WBC count became 3,000/uL. A flow cytometry from peripheral blood for acute leukemia done lately after cytoreduction was not revealing.
The rapid reduction in the WBC count in the periphery after initiation of dexamethasone and the disappearance of blast cells suggested a response similar to ALL to dexamethasone. Pathology report of the bone marrow biopsy revealed large cells with irregular nuclear appearance and nucleoli accounting for 60% of the bone marrow cellularity. Impression of acute leukemia with differential diagnosis of infiltration of high-grade NHL was stated and suggestion of the pathologist was to do the immunohistochemistry (IHC) for immune phenotyping. IHC from bone marrow biopsy was reported to be positive for CD20, BCL2, and CD10. And negative for CD3, TdT, CD34, BCL6 and MUM1. Ki-67 index was 70. The final impression of IHC of the bone marrow biopsy was consistent with diffuse large B-cell lymphoma, NOS and germinal center B-cell like( GCB) subtype.
The conflicting results from the peripheral morphology, bone marrow aspiration (BMA), flow cytometry of the peripheral blood, bone marrow biopsy (BMB), immunohistochemistry (IHC), and the rapid response to dexamethasone therapy have created diagnostic uncertainty. Finally, BMA was repeated and flow cytometry done showed 83 % of plasma cells with co-expression of CD38 and CD138 and positive for CD45, CD56, and CD200. These cells were negative for CD19, CD20, CD27, CD28, and CD117. Overall findings of flow cytometry are consistent with plasma cell neoplasm with 83% atypical plasma cells with aberrant expression of CD56 and CD200. Therefore a final diagnosis of PCL was made