Histiocytic sarcoma or Osteosarcoma? That is the question

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