A 67-year-old female presented with 3-week history of progressive fatigue, weakness, diarrhea, and fever. She had the medical history of rheumatoid arthritis, hypertension, and diabetes.
After admitted to the hospital, laboratory studies revealed the following: hemoglobin, 69 g/L; leukocytes, 4.2 × 109/L; platelets, 44 × 109/L; fibrinogen 1.6 g/L (normal range, 2-4 g/L); albumin, 26.5 g/L (normal range, 40-55 g/L); globulin, 70.8 g/L (normal range, 20-40 g/L); direct bilirubin 58 µmol/L (normal range, 0-8 µmol/L); indirect bilirubin 28 µmol/L (normal range, 3-14 µmol/L); lactate dehydrogenase, 357 IU/L (normal range, 120-250 IU/L); β2-microglobulin, 17.90 mg/L (normal range, 1.05-2.50 mg/L); C-reactive protein, 34.6 mg/L (normal range, < 8 mg/L). Coombs direct antiglobulin test was positive. Serum protein electrophoresis revealed a monoclonal protein spike (Fig. 1A). The monoclonal protein was identified as IgG lambda by serum protein immunofixation (Fig. 1B). Peripheral blood smears showed circulating enlarged immature plasma cells (20% of total white blood cells) (Fig. 1C). Other laboratory studies included negative test for anti-nuclear antibody and elevated concentration of serum IL-6 14.6 pg/ml (normal range, 0.1-2.9 pg/ml). Epstein-Barr virus (EBV) concentration detected by quantitative polymerase chain reaction was 1.04× 105.
Marrow aspirate smears demonstrated an increase in the number of plasma cells (55.0% among all nucleated cells). The plasma cells had foamy basophilic cytoplasm and open chromatin. Flow cytometric analysis of the patient’s BM showed a predominant CD45dim cell population which expressed CD19, CD38, and CD138, and did not express CD56, CD117, CD20, or CD22, and were lambda chain restricted (lambda to kappa ratio was 6) (Fig. 1D). Based on these findings, the diagnosis of plasma cell leukemia was rendered. A BM trephine biopsy revealed diffuse CD138 positive clonal plasma cells. Notably, there were infiltrating atypical lymphoid cells that were CD3 positive (Fig. E-G). Karyotypic analysis of the BM cell culture showed 46, XX in all metaphase cells analyzed (n=20). Fluorescent in situ hybridization (FISH) analysis did not show abnormality in IGH, 1q21, D13S319, P53, and RB.
Positron emission tomography (PET) computed tomography scan revealed high uptake of extensive lymphadenopathy in the chest, abdomen as well as pelvis. In addition, mild uptake of liver, spleen, and BM were seen (Fig. 2A).
A left cervical lymph node was biopsied. Unexpectedly, the structure of the lymph node was effaced and there was a diffuse infiltration of small to medium-sized atypical lymphoid cells admixed with scattered plasma cells. These lymphoid cells had clear cytoplasm, distinct cell membranes and atypical nuclears. Immunohistochemical stains demonstrated a high proliferation rate of the atypical lymphoid cells (Ki-67 index was 70%). These cells were positive for CD2, CD3, CD4, CD7, CD10 and PD-1, partially positive for CD5. They were negative for CD8, CD20, CD21, Bcl-2, PAX-5, ALK, or CyclinD1. Some cells were positive for CXCL13, Bcl-6, and EBV by in situ hybridization (EBER). The plasmacytic cells expressed CD138, CD79a, MUM1 and lambda but not kappa light chain (Fig. 2C-H). TCR gene rearrangements detected by capillary electrophoresis showed (Fig. 2B). These findings led to the diagnosis of AITL with coexisting plasma cell infiltrate for the lymph node.
There was no evidence of osteolytic lesions. Previous plasma disorders were excluded based on the patient’s medical history and clinical laboratory. Finally, the patient was diagnosed with PCL with coexisting AITL.
To further understand the molecular characteristics of the disease, WGS of CD138 purified plasma cells and CD138 negative mixed bone marrow populations (mixed BM) was performed separately by Illumina technology. Clean FASTQ sequence reads were first mapped to human genome 19 (UCSC) using Burrows-Wheeler Alignment Tool (BWA), and then local realignment was performed using the Genome Analysis Tool Kit (GATK). 464 and 540 coding non-synonymous single nucleotide variants (SNVs) for PCL and mixed BM, respectively, were obtained, 282 of which were shown in both samples (Fig. 3A). Excess of C > T and G > A nucleotide transitions were shown (Fig. 3B). Using MutSigCV, we identified 14 potential driver genes in this patient (Table 1). Functional enriched analysis of muted genes confirmed several significantly enriched pathways, including VEGF signaling.
Table 1
Significantly affected genes in both PCL and Mixed BM
PSMB4
|
TPO
|
TTC31
|
FLNB
|
CEP63
|
RANBP3L
|
PCDHA3
|
C5orf46
|
CENPQ
|
MLIP
|
TPD52L3
|
PTCH1
|
OR1L6
|
LYZL1
|
The patient was treated with one cycle of combined PD (Bortezomib 1.3 mg/m2 and Dexamethasone 20 mg/day at days 1 and 2) and Chidamide 20 mg biweekly. However, the patient developed severe pneumonia and pancytopenia, refused to receive further treatment, and discharged subsequently. She died one week after discharge.