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
How would you treat FISS?
- Surgery - 5cm + lateral surgical margins + 2 fascial planes deep
– This can involve removal of spinous processes of vertebrae
– Recurrence rates = 47% with dirty margins, 19 % with complete excision - First surgery is best chance of a good outcome
What is adjuvant Tx, When would you use it?
- Doxorubicin based chemotherapy +/or radiation therapy
- For non-resectable tumours - pre-op RT +/or chemotherapy
- For incomplete resections / marginal resections
How can you prevent FISS?
- Injections to be given in sites amenable to wide surgical excision e.g. limb or tail
- Reduce inflammatory reactions at injection sites – avoiding irritating substances where possible
- Do not over-vaccinate
What are bone tumours? What animals are predisposed?
- 85 % of skeletal tumours are osteosarcoma
- Middle age and older dogs
- Small peak in younger dogs
- Typically large breeds =
- Appendicular skeleton – metaphysis of long bones
- Front limbs 2:1 hind limbs
- Small breeds <15 kg contribute only 5 %
- 60% OSA in axial skeleton
What are clinical signs + Dx of bone tumours?
- Pain and lameness = Sudden or progressive onset, Localisable to a single bone
- Swelling
- Radiographic changes – do not differentiate tumour type
- Bone lysis
- Soft tissue swelling
- New bone – palisades perpendicular to bone – sunburst
- Periosteal elevation – Codman’s triangle
- Long zone of transition
- Does not cross joint
- Cytology or histology required to confirm diagnosis
What are Ddx for bone tumours?
- Beyond OSA - other differentials include:
- Chondrosarcoma - low metastatic risk
- Histiocytic sarcoma - metastatic risk depends upon location
- Other primaries include fibrosarcoma, haemangiosarcoma
- Other differentials =
- Myeloma / lymphoma (round cell tumour)
- Fungal osteomyelitis
- Metastatic tumours (carcinoma)
- Benign tumours / cysts
How are bone tumours treated?
*Aims = Prevention of pain, Delaying development of metastases and extending life
*Amputation =
- Most dogs tolerate amputation very well - Even large dogs and those with mild to moderate orthopaedic problems
- Patients pain free around 1 week after amputation
- Complete ambulatory adaptation takes around 1 month
How can you reduce pain with bone tumours?
- AMPUTATION should eliminate pain
- Analgesics - Use layered, multi-modal approach
- Opoids, NSAIDS, paracetamol, amantidine
- Slow bone destruction - Bisphosphonates e.g. pamidronate q 4 weeks
- Reduce sensation - Radiation therapy
- Ongoing and increasing risk of pathological fracture
- Bone stabilisation and fixation by limb sparing surgery
- Aim is to retain limb function
- High rate of infection and implant failure
** PATIENT UNLIKELY TO BE PAIN FREE **
What are osteosarcoma prognostic factors?
- Location =
- appendicular - humerus, rib, vertebral + pelvis (poorer prognosis)
- axial - skull OSA = lower metastatic rate, maxilla/ calvarium (worse px)
- Presence of metastatic disease
- Total alkaline phosphatase
What should be done for Feline osteosarcoma?
- AMPUTATION
- Much lower metastatic potential
- Amp may cure!
What are haemangiosarcomas?
- Tumours of blood vessel walls - most common in spleen
- highly invasive + metastatic
CS + Dx of haemangiosarc?
- Clinical signs usually associated with bleeding
- Shock, collapse, haemoabdomen or pericardial effusion
- Intramuscular – bruising in the dependent part of the limb
- Pericardial effusion if right auricular appendage
- Clinical pathology changes reflect bleeding and altered coagulation
- Anaemia and sometimes schistocytosis
- In early stages of bleeding - effusion and reduced TP precede measurable anaemia
- Low platelet count
- Prolonged coagulation tests and DIC
- Diagnosis usually requires histology
- Staging = imaging / cytology
What are poor prognostic factors for haemangiosarcomas?
- Tumour rupture and bleeding into the abdomen
- but diagnosis often not known at this point
- Other types of splenic tumour will also rupture
- Invasive tumours in other sites
How are primary lesions of haemagiosarc treated?
- Surgery =
- Splenectomy
- Beware of ventricular arrythmias after splenectomy
- Compartmental or wide excision in other sites
- Survival after splenectomy depends on stage
- Short if gross metastases already
- In non-visceral sites, moderately responsive to radiation
- Useful for muscular or dermal tumours
How is metastatic disease treated?
- Survival with metastasis typically 4 – 6 weeks for splenic
- Chemotherapy more useful if no gross metastasis
- Systemic chemotherapy with anthracycline based protocol
- 4 – 6 treatments at 3 weekly intervals
- For splenic HSA if no metastasis on staging sx alone MST ~ 2-4 mths; sx + Doxorubicin MST ~ 4 - 6 mths
- Metronomic chemotherapy possible option
What is thew outcomes of haemangiosarcomas?
- Splenic, intramuscular/subcutaneous and right atrial
appendage HSA have a poor px = MST less than 6 months in most studies - Intramuscular HSA in cats can be less aggressive
- Dermal HSA can have an excellent outcome = MST of around 1000 days
What is histiocytic sarcomas? Where does it affect?
- Highly metastatic sarcoma
- Arising from histiocytes – professional antigen presenting cells of the immune system
- Can affect lung, spleen, liver, bone, brain and joint
Tx of histiocytic sarcomas?
- Best outcomes are achieved with multi-modal therapy =
- Surgery, radiation and lomustine/anthracycline chemotherapy
- Dogs with gross metastasis have quite short survival = MST circa 4 – 5 months
- Dogs with complete response to therapy or no metastasis at diagnosis who have chemotherapy live much longer = MST circa 500 days
- Dogs with solitary periarticular histiocytic sarcoma
- No metastasis or disseminated disease at staging can have very prolonged survival
