Canine Lymphoma Flashcards
How are lymphomas classified? (4)
- based on anatomic form e.g. gastrointestinal, mediastinal, cutaneous
- cytologic/ histologic criteria
- immunophenotype (b cell or t cell)
- high grade vs low grade
Which lymphoma is the most common?
Multicentric (multiple origins)
Why do high grade lymphomas generally respond better to chemotherapy than low grade lymphomas?
because chemo targets rapidly dividing cells which is what high grade lymphomas are made up of (large lymphocytes= immature= rapidly dividing)
BUT low grade lymphomas still have a better prognosis
What is the major presenting sign for lymphoma?
Peripheral lymph node enlargement e.g. submandibular, prescapular, popliteal with possible hepatosplenomegaly
Why does a lymphoma often cause Polyuria/ Polydipsia?
Lymphoma releases parathyroid releasing hormone which causes hypercalcaemia
Which lymphoma (B or T cell) tends to be the most aggressive?
T cell
What do we mean by ‘Minimum Database’?
Acquired from patient to get a general idea into their health- this includes haematology (including blood smear), biochemistry and urinalysis
What will provide a definitive diagnosis for haematopoietic neoplasia and what will this look like?
Fine needle aspirate cytology of the lymph node or mass
Should see, very few small lymphocytes and a monotonous population of large lymphocytes and possibly some mitotic figures
What lymph nodes should we avoid taking cytology from and why?
Submandibular lymph nodes- they’re very reactive and so can distort figures/ samples
If the initial cytology/ FNA isn’t diagnostic what is our next option?
Biopsy of the lymph node (popliteal is the easiest to do)
What is the benefit of performing an immunohistochemistry of a tissue sample?
allows immunophenotyping- can see if its a b cell or t cell tumour
How does immunocytochemistry differ from immunohistochemistry?
allows immunophenotyping from the cytology slides (so less invasive)
What is PARR and how does it work?
PCR for Antigen Receptor Rearrangements
Uses PCR to evaluate lymphocyte receptor gene length to assess clonality levels
When is it useful to use PARR as oppose to cytology?
Useful when cytology cannot determine neoplastic vs reactive population
In PARR, a polyclonal result suggests….
What about a monoclonal result…
polyclonal= reactive
monoclonal= lymphoma
How does MHC expression affect prognosis?
Low MHC II expression in a B cell lymphoma is a negative prognostic factor
Briefly describe the initial diagnostic approach in a patient with a suspected Haematopoietic Neoplasia?
Minimum database (CBC, Biochemistry, Urinalysis)
Diagnosis with FNA cytology of peripheral lymph nodes or mass
Immunophenotyping using flow cytometry
What stage lymphoma is the most common?
3 (generalised lymph involvement)
What do we mean by substages for lymphoma?
Lymphoma is categorised 1-5 based on metastasis but can be further classified based on clinical signs e.g.
a- without systemic signs
b- with systemic signs
How do we stage a lymphoma?
Imaging- thoracic radiographs, abdominal ultrasound, CT scan
Sampling/ FNA- liver and spleen
Can we sample bone marrow to help stage the lymphoma?
You can BUT its invasive, costly and will only indicate stage 5 lymphomas of which the prognosis remains unchanged from grade 4 (so is there any point?)
Only indicated if there’s cytopenia’s or lymphocytosis
Does staging alter the treatment plan?
Only if there’s Renal, CNS or bone marrow involvement (need drugs that penetrate these better)
What is the treatment of choice for lymphoma?
Is that applicable to all?
Maximum tolerated dose multi agent chemotherapy
[can do surgery for solitary lesions or radiation therapy for nasal/ oral lymphomas]
We can give Prednisolone as palliative care and as pre treatment prior to Chemotherapy- what do we need to be aware of if we do this?
The length of the prednisolone pre treatment can upregulate chemotherapy resistance mechanisms in the neoplastic lymphocytes
