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Histiocytic sarcoma or osteosarcoma...
That is the question
Jerri McIntosh • 10yo FN Rottweiler • Referred to the SAH Oncology
service for “treatment/mgmt of an osteosarcoma”
• A month ago: suddenly yelped & became non-weight bearing lame whilst running about
• At local vet’s: radiographs (& referral) + tramadol +
advised strict rest
History • EDDU all fine • had adhered to rest instructions - only let out to
garden • left forelimb lameness improved but not entirely • generally happy at home though the tramadol
made her quite sedated
• known right forelimb osteoarthritis of 3 years duration
• has meloxicam for that
Clinical exam • bright & alert • visibly lame on left fore but mostly weight-bearing
• feeling the limb, noted a firm swelling of muscle-&-soft-tissue consistency
• local draining lymph nodes (prescaps, axillary) not palpably enlarged or firm
• NAD on chest auscultation and abdominal palpation
Radiographs sent
Ulna involvement - unusual
Radiographs sent
No pulmonary metastatic nodules were seen on chest radiographs
Our plan of action o routine bloodwork (haem & biochem)
o CT scan of elbows (both)
o CT scan of thorax
o Abdominal ultrasound scan
o FNA of the swelling • in-house + sent up to the clinical pathology unit • multiple slides to account for variation within the
lesion
The obligatory metcheck
Test results / findings • Routine blood work
o Haematology unremarkable. o Biochemistry mild elevation of AST but no increase in ALP (often seen with
OSAs)
• Abdominal ultrasound scan NAD
CT thorax (lung window)
Diagnostic imaging dx: Large aggressive soft tissue lesion with invasion and destruction of proximal left ulna - likely neoplastic.
CT forelimbs (bone & soft tissue windows)
Right elbow also showed aggressive lytic change, Centred especially on right medial humeral condyle.
CT forelimbs (bone & soft tissue windows)
FNAs & cytology • High numbers of roundish/polygonal cells, many
with multiple nuclei • Anisocytosis and anisokaryosis • Some spindle cells, many of which were binucleate
and had multiple nucleoli
• Monomorphic population of mesenchymal cells exfoliating individually and in aggregates…
• Associated with amorphous, pink extracellular matrix (osteoid or collagen)…
• Cells ranging in shape from oval to polygonal to spindle…
• Nucleus round to oval, often eccentrically located…
Types of tumours that can affect bone in dogs
• Osteosarcoma • Chondrosarcoma • Fibrosarcoma • Haemangiosarcoma • Rhabdomyosarcoma • Histiocytic sarcoma
Metastatic tumors that may present clinically as bone tumors: • Carcinomas • Plasma cell myeloma
Osteosarcomas • 85-90% of primary bone tumours • Appendicular skeleton > axial skeleton • large and giant breeds >> small breeds • Predilection sites:
away from the elbow,
towards the knee
Osteosarcomas • Transformed malignant cell is the osteoblast
• Neoplastic cells often round/ovoid
Cowell & Tyler – cells from a canine osteosarcoma
and not
Histiocytic sarcomas • transformed malignant cells
are interstitial dendritic antigen-presenting cells (APCs)
• Uncommon in dog population as a whole
• But tremendously common in certain breeds Cowell & Tyler – aspirate from a histiocytic sarcoma
Round, discrete cells!
Histiocytic sarcomas • 2 forms
o Localised • deep limb musculature and periarticular • Highly malignant and metastatic
o Disseminated
• both localised and disseminated forms carry quite a guarded prognosis
Back to Jerri…
Histiocytic
sarcoma? Osteosarcoma?
Jerri’s FNA slides -‐‑ discussion
• Cytology can be rewarding but also confusing, especially to the unpractised eye
• Special cytochemical stains available o BCIP/NBT solution stains ALP in osteoblasts o ANBE stains intracellular esterase enzymes that are present in cells of dendritic/
monocytic origin
• Variation amongst different sites of the lesion sampled
Provisional diagnosis: Lytic bone tumour of left ulna.
Sarcoma.
Treatment options • Amputation + follow-up with chemo = first-line
• Radiotherapy
• More analgesics o e.g. tramadol , fentanyl patches
• Bisphosphonates
o help reduce bone lysis and pain
Palliative intent
Considerations • Tried simulating a left forelimb amputation by
bandaging it up
• The worrying CT scan findings o Pulmonary metastases – prognosis slightly poorer (though early stage
metastatic disease as not detected on radiography yet) o Compromised right elbow – arthritic change + possible neoplasm as well
Recommendations and owner’s decision
• Radiotherapy • +/- chemotherapy to follow
o explained would be much less effective as, even though irradiated, whole mass still there
• +/- bisphosphonates and additional analgesic medication
Jerri went home on metacam SID and she’s scheduled to come in week commencing 15 sept for a 5d course
of radiotherapy (palliative intent)
Updates • Owner has called on 2 occasions
o Worried about Jerri’s lameness o Wondering if can XRT both forelimbs – going to give it a go
• Jo also thinking of doing a repeat FNA (just for interest’s sake) o Definitive diagnosis more important only if owners decide to follow on with
chemo o As would influence choice of agent
• OSA à carboplatin • Histiocytic sarcoma à lomustine
Key points • Although osteosarcomas are the most
commonly occurring primary bone tumours, if lesion is not in usual predilection site, then also consider: o Histiocytic sarcomas – particularly in Bernese Mountain
Dogs, Flat coated retrievers, Rottweilers & Golden Retrievers
o Secondary mets – esp from mammary/prostatic carcinomas and multiple myeloma
• Always take radiographs of (or CT scan) opposite limb as well ! o Very helpful for comparison + evaluating patient
suitability for surgery
Julie, who initially saw Jerri Gawain Hammond, for imaging interpretation advice
Jo Morris, for going over the case with me
Everyone here, for listening J