EQUINE | CPD of age ), or only a single focus ( more common in horses > 16 years of age ), with the small intestine being more commonly involved than the large intestine . This form of lymphoma is a disease of old horses with mean age of onset at 16 years .
EQUINE | CPD of age ), or only a single focus ( more common in horses > 16 years of age ), with the small intestine being more commonly involved than the large intestine . This form of lymphoma is a disease of old horses with mean age of onset at 16 years .
Spread from the intestine to involve mesenteric lymphnodes and other visceral organs makes it difficult to distinguish alimentary lymphoma from multicentric disease . The majority of intestinal lymphomas are of T- cell origin , while those of B-cell origin may be associated with hypergammaglobinaemia .
Weight loss , lethargy and anorexia are the most common presenting signs with abdominal pain and / or diarrhea caused by malabsorption , along with protein losing enteropathy , being less frequently observed .
Mediastinal Lymphoma
Mediastinal ( thymic / thoracic ) lymphoma is the most common neoplasia of the chest cavity of horses . Dyspnea , coughing , distention of the jugular vein and pleural effusions may be observed in addition to the general signs of lymphoma . Severe bradycardia associated with complete atrioventricular block has been described in individual cases .
Cutaneous Lymphoma
Primary cutaneous lymphoma is rarely seen in horses and most cases with skin lesions are part of a generalized multi-systemic disease . Less than 5 % of equine lymphomas are classified as primary cutaneous . Most are of T cell origin with many progressing to a chronic lymphocytic leukemia .
T-cell rich large B-cell lymphomas ( TCRLBL ) are the predominant subtype of lymphoma involved in equine cutaneous lymphoma with T-cell lymphoma ( CTCL ) being the second most common subtype . Less commonly documented subtypes include diffuse large B cell lymphoma and anaplastic large T-cell lymphoma . Quarter horses almost exclusively develop TCRLBL while CTCL are more common in Thoroughbreds compared to other breeds . TCRLBL usually present as multiple masses while CTCL are more commonly solitary nodules .
Clinical presentation is of alopecic , ulcerative and exudative skin lesions with anatomical predilection sites being the head , limbs , trunk and perineum . TCRLBL have significantly longer survival times without local recurrence , suggesting that complete local excision maybe an effective therapy , the prognosis with CTCL is less favorable . In mares cutaneous lesions are reported to regress during pregnancy only to re-appear after foaling .
Solitary Lympomas of extra-nodal sites
There are many published case reports documenting solitary lymphoid tumours of the spleen , palate , nasopharynx , nasal passage , sinus , tongue , meninges and pelvis . Splenic lymphoma is an isolated lesion involving the lower part of the spleen and may attain very large size . Animals normally present with a responsive hemolytic anaemia due to trapping of erythrocytes in adjacent hyperplastic splenic tissue . Leukemia is however absent . Tumours are usually large B cell and they usually remain restricted to the spleen .
Diagnosis
Surgical , laparoscopic or ultrasonographic-guided biopsies placed in 10 % buffered formalin for histology remains the gold standard diagnostic procedure for the confirmation of lymphoma in the equine species . In addition to evaluation of morphological characteristics of lymphocytes , histology enables assessment of architectural changes , uniformity of the lymphocyte population and establishment of the mitotic index , all of which are crucial for the confirmation of the diagnosis of lymphoma and staging of the tumour . Cytological examination of fine needle aspirates or
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