Diseases of the lymph nodes

Question 1

How are usually disorders of the lymph nodes characterized

Answer 1

Disorders of the lymph nodes are usually characterized by:
- changes in size (i.e., lymphadenomegaly)

- changes in consistency

- pain or heat on palpation

Question 2

What is the anatomy of a lymph node

Answer 2

Lymph nodes are composed of:
- an outer cortex: primarily made up of B-cell follicles surrounded by a zone of T-cells

- an inner cortex (or paracortical area): containing small T-cells and antigen-presenting macrophages

- a medulla consisting of cords (comprised of macrophages, lymphocytes, plasma cells) intertwined with medullary sinuses containing lymph fluid

Question 3

How does a lymph node function

Answer 3

Afferent and efferent blood vessels enter and exit at the hilus

Afferent lymphatic vessels enter at various points of the periphery and the lymph travels towards the hilus, filtering its way through the cortical, paracortical and medullary regions where particulate material, abnormal cells and a variety of foreign antigens are scrutinized by all of the components of the specific immune response present

Finally, the lymph exits the node via the efferent lymphatic vessel, where it continues on its way to eventually be dumped into the venous circulation in the cranial vena cava

Question 4

What would be your differentials for regional or solitary lymphadenopathy

Answer 4

Neoplastic:
- Metastatic carcinoma/sarcoma
- hemolymphatic

Infectious:
- bacterial (e.g., bacterial lymphadenitis, mycbacteria)
- viral (e.g., URT disease)
- fungal (e.g., cryptococcosis, sporotrichosis)

Inflammatory:
- eosinophilic granuloma complex

Other:
- plexiform vascularization idiopathic
- lymph node hyperplasia

Question 5

What would be your differentials for generalized lymphadenopathy

Answer 5

Neoplastic:
- lymphoma
- myeloproliferative disease
- multiple myeloma
- systemic mastocytosis

Infectious:
- systemic bacterial diseases (e.g., mycobacteriosis, salmonellosis)
- systemic fungal diseases (e.g., cryptococcosis, histoplasmosis, sporotrichosis)
- viral (e.g., FeLV, FIV, FIP)
- post-vaccinal (uncommon)

Other:
- reactive hyperplaasia
- idiopathic generalized reactive lymphadenopathy
- hypereosinophilic syndrome

Question 6

Give the key features for idiopathic generalized reactive lymphadenopathy

Answer 6

Describe in otherwise healthy, young cats

Generalized lymphadenopathy with some histopathological features of lymphoma

In many cases the disease appeared to spontaneously resolve after a few weeks to months without chemotherapy