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Histiocytic sarcoma or Osteosarcoma? That is the question.

Francesca Tee
Francesca Tee

This document discusses the case of a 10-year-old female Rottweiler named Jerri who presented with sudden lameness in her left forelimb. Radiographs and CT scans revealed an aggressive soft tissue lesion invading and destroying the proximal left ulna, likely a neoplasm. Fine needle aspirates of the swelling showed round cells consistent with either osteosarcoma or histiocytic sarcoma. Given the patient's breed and unusual location of the lesion, histiocytic sarcoma could not be ruled out. Treatment options of amputation, radiation therapy, chemotherapy or palliative care were discussed. The owner elected to pursue radiation therapy with the goal of palliation.

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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 vets: 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 / 鍖ndings ≒ 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 油敬庄稼糸看敬)
Histiocytic sarcoma or Osteosarcoma? That is the question.
Histiocytic sarcoma or Osteosarcoma? That is the question.
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 a鍖ect 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?
Jerris FNA slides -足 discussion ≒ Cytology can be rewarding but also confusing, especially to the unpractised eye ≒ Special cytochemical stains available o BCIP/NBTsolution 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 owners 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 shes 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 Jerris lameness o Wondering if can XRT both forelimbs going to give it a go ≒ Jo also thinking of doing a repeat FNA (just for interests sake) o Definitive diagnosis more important only if owners decide to follow on with chemo o As would influence choice of agent ≒ OSA carboplatin ≒ Histiocytic sarcoma 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

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Histiocytic sarcoma or Osteosarcoma? That is the question.

  • 1. Histiocytic sarcoma or osteosarcoma... That is the question
  • 2. 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 vets: radiographs (& referral) + tramadol + advised strict rest
  • 3. 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
  • 4. 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
  • 6. Radiographs sent No pulmonary metastatic nodules were seen on chest radiographs
  • 7. 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
  • 8. Test results / 鍖ndings ≒ 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
  • 9. CT thorax (lung 油敬庄稼糸看敬)
  • 12. Diagnostic imaging dx: Large aggressive soft tissue lesion with invasion and destruction of proximal left ulna - likely neoplastic. CT forelimbs (bone & soft tissue windows)
  • 13. Right elbow also showed aggressive lytic change, Centred especially on right medial humeral condyle. CT forelimbs (bone & soft tissue windows)
  • 14. 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
  • 15. Types of tumours that can a鍖ect bone in dogs ≒ Osteosarcoma ≒ Chondrosarcoma ≒ Fibrosarcoma ≒ Haemangiosarcoma ≒ Rhabdomyosarcoma ≒ Histiocytic sarcoma Metastatic tumors that may present clinically as bone tumors: ≒ Carcinomas ≒ Plasma cell myeloma
  • 16. 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
  • 17. Osteosarcomas ≒ Transformed malignant cell is the osteoblast ≒ Neoplastic cells often round/ovoid Cowell & Tyler cells from a canine osteosarcoma and not
  • 18. 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!
  • 19. 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
  • 20. Back to Jerri Histiocytic sarcoma? Osteosarcoma?
  • 21. Jerris FNA slides -足 discussion ≒ Cytology can be rewarding but also confusing, especially to the unpractised eye ≒ Special cytochemical stains available o BCIP/NBTsolution 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.
  • 22. 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
  • 23. 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
  • 24. Recommendations and owners 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 shes scheduled to come in week commencing 15 sept for a 5d course of radiotherapy (palliative intent)
  • 25. Updates ≒ Owner has called on 2 occasions o Worried about Jerris lameness o Wondering if can XRT both forelimbs going to give it a go ≒ Jo also thinking of doing a repeat FNA (just for interests sake) o Definitive diagnosis more important only if owners decide to follow on with chemo o As would influence choice of agent ≒ OSA carboplatin ≒ Histiocytic sarcoma lomustine
  • 26. 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
  • 27. 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