EQUINE | CPD
EQUINE | CPD
lymphnode impression smears only provides morphological details of cells in isolation , rending cytological examination inconclusive in many instances , due to the complexities of distinguishing lymphoma from atypical lymphoid hyperplasia .
A further advantage of formalin-fixed tissues for histology is that immunophenotyping , tumour proliferation rate and immunohistochemical ( IHC ) analysis for progesterone receptors can be performed . Immunophenotyping allows for classification of the tumour as either B or T cell origin . Multicentric and alimentary lymphomas are predominantly T cell origin , mediastinal lymphomas are exclusively T cell , cutaneous tumours are either T cell rich B cell lymphomas or of T-cell origin while solitary tumours of extra-nodal sites may be of B or T cell origin . In general T cell lymphomas are more aggressive and carry a poorer prognosis than B cell lymphomas .
Application of IHC stains to asses tumour proliferation rate ( Ki67 ) is used to assist in prognostication and to monitor response to therapy . However , correlation between the recorded replication rate , prognosis and response to treatment is currently unknown in the horse and further data needs to be collated before any recommendations can be made based on the tumour proliferation rate .
In some mares , cutaneous lymphoma is reported to regress during pregnancy and so application of IHC stains for progesterone receptors on tumour cells , might have some therapeutic implications .
Therapy
Current therapy options applied include surgical excision , radiation therapy , chemotherapy and hormone therapy in mares with cutaneous lymphoma . However , little is known about the efficacy of these various treatments , treatment protocols are based on anecdotal data and the majority of cases are usually only diagnosed in advanced stage of the disease . Response to therapy is therefore disappointing in many instances , with the exception of T cell rich B cell cutaneous lymphomas which exhibit long survival times following complete local excision .
REFERENCES
1 . Durham A C , Pillitteri C A et al . 2013 . Two hundred three cases of equine lymphoma classified according to the World Health Organization ( WHO ) Classification Criteria . Veterinary Pathology 50:86-93 . 2 . Meyer J , Delay J et al . 2006 . Clinical , laboratory and histopathologic features of equine lymphoma . Veterinary Pathology 43:914-924 . 3 . Miller C A , Durham A C et al . 2015 . Classification and clinical features in 88 cases of equine cutaneous lymphoma . Journal of Veterinary Diagnostic Investigation 27:86-91 . 4 . Taintor J & Schleis S . 2011 . Equine lymphoma . Equine Veterinary Education 23:205-213 . 5 . Valli V E O , Kiupel M et al . 2016 . Hematopoeitic System . In : Jubb , Kennedy & Palmers Pathology of Domestic Animals 6th edn . 237-238 . Elsevier , St Louis . 6 . Cowell R L , Tyler R D et al . 2002 . Lymph Nodes . In : Diagnostic Cytology and Haematology of the Horse . 2nd edn . 99-106 . Mosby , St Louis .
Equine lymphoma – Questions
Question 1 Which of the following tissues does equine lymphoma not commonly arise from ? A . Lymphnode . B . Spleen C . Gut associated lymphoid tissue D . Lung E . Bone marrow .
Question 2
• Volume 19 no 1 • February 2017 • 33