oncology SA

Lymph node sampling

·    Indications: if enlarged, suspect underlying infectious disease (e.g. FIP, fungi, leishmania), staging of malignant disease (can see metastatic spread)

·    Precautions when sampling:

o  Non-suction technique to minimise blood contamination

o  Spread gently on slide as fragile cells

o  If enlarged, don’t sample centre as likely necrotic

o  Take sample BEFORE giving steroids

·    Normal LN – 90% small lymphocytes, 5-10% small + medium lymphocytes

o  + plasma cells, macrophages, mast cells, neutrophils (rare)

Lymph node pathology

·    Reactive hyperplasia – increased large lymphocytes, increased plasma cells (vacuole)

·    Lymphadenitis

o  Neutrophilic – lots of neutrophils (causes: bacterial, immune-mediated, neoplastic)

o  Eosinophilic – lots of eosinophils (causes: hypersensitivity reaction, parasites, idiopathic, paraneoplastic)

o  Granulomatous/pyogranulomatous – incr. macrophages +/- neutrophils (causes: chronic inflammatory conditions, e,g. fungal infections, FIP, leishmaniasis)

·    Lymphoma – lots of large immature lymphocytes (bigger than RBCs), more mitosis, macrophages

·    Metastatic neoplasia – cells present that shouldn’t be (e.g. mast cells)

Thymoma vs lymphoma

·    Thymoma – originates from epithelial cells, see epithelial cells, small lymphocytes, occasional mast cell

o  Diagnosis: imaging (see mass in cranial mediastinum), cytology, histopathology

o  Treatment: surgery

·    Lymphoma – originates from lymphocytes, see lots of large lymphocytes

o  Diagnosis: imaging (see mass in cranial mediastinum), cytology, histopathology

o  Treatment: chemotherapy (surgery not suitable as entire lymphatic system affected)

Myeloid neoplasia’s

·    Myeloid leukaemia – acute or chronic

·    Mast cell tumour

o  Granulocytes that undergo malignant transformation, locally invasive, risk of degranulation

o  Treatment: masitib, toceranib, tigilanol tigilate

·    Histiocytoma

o  Usually benign, seen in dogs <2yr, regress independently

·    Transmissible venereal tumour

o  Infected tumour, transmitted during mating

o  Treatment: chemotherapy (vincristine)

Lymphoid neoplasia’s

·    Lymphoid leukaemia – acute or chronic

·    Plasmacytoma

o  Benign cutaneous mass, can be locally invasive, found on skin, oral cavity, rectal mucosa

·    Lymphoma

o  Develops from malignant transformation of lymphocytes – can occur anywhere

o  Multicentric lymphoma – affects multiple lymph nodes

Splenic mass

·    Most common: haemangiosarcoma (dogs), splenic MCT (cats)

·    Presentation: abdominal distension, pain on abdo palp, anaemia, lethargy, cough (due to metastatic spread), acute emergency/collapse (if torsion and blood supply cut off)

·    Prognosis: splenectomy = 3m, splenectomy + chemo = 6m

Paraneoplastic syndromes

·    Hypercalcaemia

·    Hyperviscosity – blood becomes thick ® harder to move through vessels ® high BP

·    Hormones – some tumours release oestrogen ® bilateral symmetrical alopecia in ovarian tumours, hyperoestrogenism in Sertoli cell tumours

·    MCT – mast cells release histamine, degranulation ® itching + also V+/D+

Staging a tumour

·    Haematology and biochemistry – check for bone marrow involvement, liver parameters

·    Ultrasound – to screen liver and spleen

·    Thoracic radiography – check if mets to the liver

To stage a tumour:

·    Tumour – grade, size, ulceration, how fixed

·    Lymph node – metastasis to local LN?

·    Distant metastasis – other LNs in body, other organs, e.g. liver, spleen, lungs

Management of tumours

·    Surgical excision

o  Radical – e.g. amputation

o  Curative intent – 3cm lateral margins, 1 fascial plane

o  Marginal surgery – leave microscopic remnants behind

o  Cytoreductive therapy – leave macroscopic remnants behind

·    Steroids – reduce inflammation, provide analgesia

o  But limited effects, unless use alongside chemotherapy

·    Chemotherapy:

o  Medical therapy

o  Cytotoxic drugs

o  Anti-neoplastic agents

o  Immunosuppressive drugs

o  Considerations: appropriate restrain, extravasation (make sure in vein), side effects (reduced immunity, whisker/fur loss, V+/D+)