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An Urban Experience
Lymph node biopsy is ideally performed for histologic grading but is often only collected when cytology was inconclusive. Baseline chest radiographs and abdominal ultrasound are recommended for staging purposes to determine extent of disease. While stage is prognostic,
I also find it valuable to have these baseline imaging tests to be able to compare treatment response or progression. Bone marrow cytology is also considered part of the basic staging but it is often not done is
the majority of cases, factoring in the additional cost and sedation for most cases. Bone marrow cytology is of less clinical utility in most cases. However, if
there are cytopenias and/or a lymphocytosis, a bone marrow should be considered to identify bone marrow involvement.
To stage or not to stage? Complete lymphoma staging includes lymph node cytological confirmation, CBC, chemistry panel, urinalysis, lymph node histology, urinalysis, thoracic radiographs, abdominal ultrasound, bone marrow cytology and phenotyping. These tests
are useful and informative, as they provide prognostic factors and a baseline for a patient’s response. These tests can also help determine if there large tumor burden and risk for acute tumor lysis syndrome with induction chemotherapy. Still, we must consider the owner’s financial issues. While it is ideal to perform all the tests, we can also consider each test on a case by case basis and help the owner make an educated decision. We can treat without but review pros and cons with the owner and let owner make educated decision and maybe choose more important tests for that dog.
NIH WF & Kiel System most useful, and both describe architecture and cell morphology, including mitotic index, cell size, and cell shape. Why do I care about histology? It’s prognostic. Positive: Low grade LSA, Including mantle-zone, follicular, T-cell. But low grade LSA may only partially respond to chemotherapy and is often incurable. Negative: intermediate and high grade LSA BUT have a high mitotic rate & are more likely to completely respond to chemotherapy.
Phenotype: 60-80% of LSA are B-cell, and this is an important positive predictor, associated with higher rate of CR, longer remission, increased ST, and most high grade are B-cell. Breed prevalence with B-cell includes Cockers and Dobies. Goldens have equal B and T-cell. 10-38% of LSA are T-cell, and this is an important negative predictor, associated with lower rate of CR, shorter remission, shorter ST, and tends to be associated with hypercalcemia. Boxers are over-represented.
Flow Cytometry (FCM) involves staining live cells with labeled antibodies that bind to cell surface proteins. These live cells are suspended in liquid (saline, tissue culture media). Different types of lymphocytes express
different proteins. Flow cytometer tells us how many cells of each type are present and can determine the lineage of the cells present. Flow could not identify LSA in 30% of newly diagnosed cases
PARR: PCR Antigen Receptor Rearrangement is a polymerase chain reaction (PCR) assay that amplifies DNA with PCR primers in the dog or cat. It tells us if
the majority of cells in the sample are clonal: same original clone - most consistent with neoplasia, or from multiple clones/polyclonal - lymphoid proliferation -
most consistent with a reactive process, It is useful to determine: whether lymphoid neoplasia, phenotype (B vs. T), and to monitor for MRD in treated patients, It must be interpreted with history, clinical signs, cytology, flow cytometry, IHC.
For sensitivity & specificity, both are ~90% in dogs, and it is more sensitive for circulating cells > blood, bone marrow. In cats, it is better for T cell (89%, 80%) vs B-cells (60%, 70%). FCM and PARR are NOT useful for neutrophilia to r/o chronic myelogenous leukemia, when hypercalcemia is only sign, not helpful on LN, fluid, etc., or as a screening test for healthy dogs and cats without clinical signs.
Prognostic factors: There are many prognostic factors, but the more significant predictors include:
• Phenotype: B-cell is better than T-cell. 60-80% are B-cell and this is associated with higher rated of CR, longer remission rates, and increased ST. Most high grade LSA are B-cell.
• Histologic grade: high grade has better CR rate than low grade, but low grade often has comparable survival times with less intensive chemotherapy protocols.
• Administration of prednisone prior to chemotherapy is a negative predictor
• Substage: clinically healthy dogs tend to do better than sick dogs
• Higher stage (stage IV and V) tend to do worse than lower stage (I to III)
• Hypercalcemia: negative predictor due to association with T-cell phenotype
• Mediastinal mass: negative predictor due to association with T-cell phenotype
Remember, prognostic factors cannot predict an individual’s response, and lymphoma is typically treatable and rewarding to treat for the patient, owner and the veterinarian.
Treatment Modalities
Treatment pearls Chemotherapy is the mainstay of therapy to promote a rapid, durable and complete remission (CR), while maintaining a good to excellent quality of life even during chemotherapy. Complete

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