Pathology of the Lymphoreticular System

Question 1

What thymic pathology is associated with an FeLV infection?

Answer 1

Thymic Lymphoma

Question 2

How can we best diagnose Thymic Lymphoma?

Answer 2

Radiographs
Pleural effusion cytology- will see increased lymphoblasts

Question 3

Which breeds are predisposed to Thymoma’s?

Answer 3

GSD’s and Labrador Retrievers

Question 4

What is a thymoma?

Answer 4

neoplasia of the thymic epithelial cells

Question 5

What pathologies are commonly associated with Thymoma’s and why? (2)

Answer 5

Hypercalcaemia- thymoma produces PTH peptide- this peptide binds to the PTH receptor and releases calcium from mineral stores
Myasthenia Gravis - thymoma causes an overproduction of autoreactive T cells which drive autoantibody responses against the Ach receptor

Question 6

Through which ducts do lymphocytes return to the blood stream?

Answer 6

Exit the lymph node via the efferent lymphatics and return to the bloodstream via the TRACHEAL/ THORACIC DUCTS

Question 7

Blockage of lymphatics can lead to…

Answer 7

Peripheral Oedema

Question 8

What can a perforation in the thoracic duct lead to and why?

Answer 8

Chylothorax- the thoracic duct is where lymph returns to the bloodstream, damage here can cause lymph to leak into the thorax

Question 9

What is the key indicatory of Lymph Node disease?

Answer 9

Lymphadenopathy- lymph node enlargement

Question 10

What would you expect to see on the Haematology of an animal with Lymphadenopathy caused by a Bacterial infection?

Answer 10

Neutrophilia with left shift (immature neutrophils)

Question 11

In cases of viral disease, how will this present on Haematology?
What about parasitic disease?

Answer 11

Viral- Lymphopenia
Parasitic- Eosinophilia

Question 12

You take a biopsy of an abnormally large lymph node- what are the four main differential diagnoses’ and what changes would you expect to see in the lymph node architecture in relation to the diagnosis?

Answer 12

1. Reactive lymph node- normal response to infection- increased cellularity shown by secondary follicles and germinal centres
2. Lymphadenitis- due to infection in the lymph node causes areas of necrosis and pyogranulomatous inflammation
3. Primary neoplasia- lack of normal architecture
4. Secondary neoplasia- normal tissue with neoplastic infiltration

Question 13

What may cause Diffuse Splenomegaly (enlargement of the spleen)? (4)

Answer 13

Venous congestion
Lymphoid hyperplasia due to infection, inflammation
Amyloidosis
Neoplasia e.g. lymphoma, myeloma

Question 14

What other pathological symptom (not diffuse splenomegaly) may we see in the spleen when it is diseased?

Answer 14

Nodular Splenomegaly- diseases include Swine Fever, Johne’s, Babesia, Leishmania etc.