Hematopathology / LEUKEMIC MANTLE CELL LYMPHOMA WITH A CD5–, CD10+ BLASTOID COMPONENT

Materials and Methods Flow cytometric immunophenotyping analysis was performed according to previously described methods.11 Hematopathology / CASE REPORT Am J Clin Pathol 2004;122:122-127 123 123 DOI: 10.1309/UD2C6JVPWHXQQ217 123 © American Society for Clinical Pathology Following isotonic lysis, nucleated cells were stained with fluorochrome-conjugated antibodies to the following antigens: CD3, CD5, CD10, CD11c, CD14, CD16, CD19, CD20, CD22, CD23, CD38, CD45, and κ and λ immunoglobulin light chains. All antibody conjugates were obtained from Becton Dickinson Biosciences, San Jose, CA. Analysis was performed on a FACSCalibur instrument (Becton Dickinson), and the data were processed using CellQuest software (Becton Dickinson). Immunoperoxidase stains were performed on the B-5–fixed, decalcified, paraffin-embedded bone marrow biopsy specimen using previously described techniques.12 The antibodies to CD3 (polyclonal), CD20 (L26), bcl-2 (124), bcl-6 (PB-B6p), and cyclin D1 (DCS-6) were obtained from DAKO, Carpinteria, CA. The antibodies to CD5 (4C7) and CD10 (56C6) were from Novocastra, Burlingame, CA. Fluorescence in situ hybridization (FISH) studies for CCND1-IgH gene fusion were performed on the peripheral blood specimen using different colored, directly labeled, gene-specific probes (Vysis, Downers Grove, IL) according to previously described methods.4 Case Report A 64-year-old woman with a 29-month history of “chronic lymphocytic leukemia” sought care because of new-onset fatigue and lassitude. The previous diagnosis of chronic lymphocytic leukemia was based on persistent peripheral blood lymphocytosis; immunophenotyping studies reportedly were not performed. The physical examination revealed marked splenomegaly without appreciable lymphadenopathy. Peripheral blood CBC analysis showed a marked leukocytosis (WBC count, 378,000/μL [378.0 × 109/L]) associated with anemia (hemoglobin, 7.7 g/dL [77 g/L]) and thrombocytopenia (platelet count, 72 × 103/μL [72 × 109/L]). An initial manual differential count was performed, and 80% (0.80) of the WBCs were thought to represent lymphocytes and 10% “blasts.” Based on these findings, the possibility of acute leukemia was raised, and peripheral blood and bone marrow biopsy specimens were submitted for analysis. On review of the peripheral blood smear, 2 morphologically distinct groups of lymphocytes were identified. One was composed of cells having small nuclei with condensed chromatin and irregular nuclear contours and the other of cells having larger nuclei with delicately reticulated chromatin, multiple nucleoli, and densely basophilic, vacuolated cytoplasm ❚Image 1❚. These cell populations were present in relatively equivalent proportions. Flow cytometric analysis revealed the peripheral blood leukocytes to be largely composed of CD19+ B cells with bright, monoclonal, κ sIg light chain expression ❚Image 2A❚. However, despite the relatively uniform staining intensity for CD19 and κ light chain, it was evident that 2 immunophenotypically distinct monoclonal B-cell populations were present. One cell population, located primarily in the small lymphocyte gate (forward scatter and side scatter gating), stained brightly with antibodies to CD20 and CD45 and expressed CD5; these cells did not coexpress CD10 or CD23 and showed partial, dim staining with antibodies to CD38 ❚Image 2B❚. The second cell population, found in the large lymphocyte gate, expressed CD10 and CD38 and was CD5– and CD23– ❚Image 2C❚. In comparison with the CD5+ cells, this second cell population showed slightly diminished staining intensity for CD45. A diagnosis of MCL was considered based on the presence of clonal, CD5+ B cells; however, it was unclear whether the CD10+CD5– B-cell clone was a related or second, distinct process. FISH studies performed on the peripheral blood specimen demonstrated CCND1-IgH gene fusion in 93% of 500 analyzed nuclei, confirming a diagnosis of MCL. The percentage of FISH-positive cells was approximately equal to the percentage of peripheral blood lymphocytes by manual differential (95% [0.95]), indicating that CCND1-IgH fusion was present in both the CD5+ and CD10+ lymphocyte subsets. The bone marrow biopsy specimen was infiltrated densely by neoplastic lymphocytes having blastoid cytologic features with intermediate-sized nuclei, speckled chromatin, ❚Image 1❚ Peripheral blood smear showing 2 populations of abnormal lymphocytes: one with small nuclei and condensed chromatin and the other with larger nuclei, more open chromatin, and dense, basophilic cytoplasm (WrightGiemsa, ×1,000). Morice et al / LEUKEMIC MANTLE CELL LYMPHOMA WITH A CD5–, CD10+ BLASTOID COMPONENT 124 Am J Clin Pathol 2004;122:122-127 124 DOI: 10.1309/UD2C6JVPWHXQQ217 © American Society for Clinical Pathology 0 200 400 600 800 1,000 104