Sarcomas Flashcards
What is a sarcoma?
Subtypes?
- a malignant cancer that arises from transformed cells of mesenchymal origin
- Mesenchyme – cells of connective / structural tissues
Subtypes vary by cell of origin
* Bone - osteosarcoma
* Connective tissue - soft tissue sarcoma, fibrosarcoma, myxosarcoma
* Peripheral nerves - peripheral nerve sheath tumour
* Blood vessels - haemangiosarcoma
* Muscle – rhabdomyosarcoma (striated muscle rare), leiomyosarcoma (smooth muscle - uncommon)
* Fat – infiltrative lipoma, liposarcoma
* Cartilage - chondrosarcoma, synovial cell sarcoma
* (Lymphatic and haematopoetic cells – many of these tumours are considered separately – based on behaviour)
What is general behaviour of sarcomas?
- Locally invasive
*Metastatic risk varies with tumour type (osteosarc, haemangiosarc = v high) + Grade
How would you assess sarcomas?
- Clinical examination
- Diagnosis = FNA + cytology, Biopsy and histology, +/- IHC
- Staging - is there evidence of metastasis ?
- Aspiration of local lymph nodes
- Imaging dependent upon tumour type
- Sample other abnormalities identified on examination
- Co-morbidities
How would you perform primary tumour imaging?
- Radiographs are relatively insensitive
– >60% of mineral content of bone must be lost for lysis to become apparent
– All soft tissues except fat look the same - CT better
– Better appreciation of osteolysis or new bone production
– Many more shades of grey
– Surgical planning
– Radiation planning - MRI – Excellent for surgical planning esp trunk/body wall
What is most likely location of mets for sarcoma?
- Lungs
What are soft tissue sarcomas?
- Tumours of mesenchymal origin
- Account for 9 -15% of all canine tumours
- Middle to large breeds may be predisposed
- Median age 8 -11 years
- Some breed predilections – Fibrosarcomas in Retrievers
- Younger animals in predisposed breeds
What is surgical Tx?
- Tumours = grow along path of least resistance, often have a pseudocapsule (do not try to ‘shell out’)
- Complete excision important to outcome
- Ideal surgical margins = 3 cm lateral and 1 fascial plane
beyond the extent of tumour
How are margins of excision assessed?
- Most common = CARDINAL = 3 cross sections
- Bread loafing (cut like you would a loaf)
- Shaved margins - expensive
What is incomplete excision?
- Residual tumour tissue still in animal = tumour likely to recur
- Tumour cells within <3mm of tissue edge
- Probability of recurrence depend on tumour type + grade
What can be done if incomplete excision + microscopic residual disease?
- Further wide surgical excision
- Adjuvant radiation therapy
- Active monitoring - high risk (only considered when chance of recurrence is low)
What are prognostic factors for post tumour removal?
- Successful surgery = MST >4years
Progonstic factors =
* Tumour grade and mitotic rate
* Tumour size
* Tumour location
* Achieving local control of the tumour
What should be done with non-resectable tumours?
- Refer to specialist?
- Reduce tumour to microscopic disease - followed by RT / chemotherapy
- Primary RT = less effective
- Anti-metastatic treatment - for high grade soft tissue sarcomas
What are feline injection site sarcomas?
- Tumours develop at sites where cats typically get injections
- Research has shown location of tumours change with vaccine practices
- Development associated with certain vaccines (Rabies / FeLV) but can be seen in cats who have never had these
- Histologically =
- Malignant fibroblasts
- Inflammation – often high lymphocyte component
- Macrophages taking up foreign material thought to be adjuvant / carrier
How would you assess a feline injection site sarcoma?
- Examination – Usually firm cutaneous or subcutaneous mass
- 3-2-1 rule for investigation = USE FOR DIAGNOSIS
– Any mass present for 3 months or longer
– Any mass greater than 2cm diameter
– Any mass that continues to increase in size 1 month after injection - incisional Biopsy
- Advanced imaging - assess size + margins (highly invasive)
Why would you not perform excisional biopsy?
- Almost guarantee treatment failure
