Ultrasonography of Osteosarcoma in Dogs
Sonography Atlas of Dogs

Abstract

Osteosarcoma is the most frequent bone tumor in dogs representing about 85% of the tumors in bones. It’s
occurrence in the axial skeleton is rare and it’s more frequent in females. The prognosis is poor with a great
metastatic  occurrence.  A  white  shepherd  dog,  male,  8 years  with  a  large  tumor  in  the  frontal  region,  quick growth, rigid consistency and pain by manipulation, was brought to the clinic. Surgical excision was performed and histopathological examination confirmed the suspected diagnosis as osteosarcoma. The patient was referred for chemotherapy. The tumor showed up again in the same location requiring new surgical procedure, but there was never evidence of metastasis in this case.

Introduction
Osteosarcoma  (OSA)  or  osteogenic sarcoma (Daleck  et  al.,  2006)  is  the  most  common  primary bone   cancer   diagnosed   in   dogs,   a   malignant mesenchymal  tumor  from  the  primitive  anaplastic bone  cell,  characterized  by  an  extracellular  matrix osteoid   production,   which   is   their   histological differentiation  (Neuwald  et  al.,  2006).  It  represents around 85% of the bone tumors (Costa et al., 2001, Gomes et al., 2008, Oliveira and Silveira, 2008). Its incidence in the axial skeleton is 25% (Cavalcanti et al.,  2004),  most  reported  in  females  (Daleck  et  al.,
2006)   and   occurs   principally   in   older   dogs   of medium  size  (Neuwald  et  al., 2006).  In  a  study  of 116  dogs  affected  with  axial  osteosarcoma,  12% were  located  on  the  skull  and  it  was  reported  at lower  jaw  (27%),  maxillary  (22%),  spine  (15%), ribs (10%), nasal cavity and paranasal sinuses (9%) and  pelvis  (5%)  (Gomes  et  al.,  2008, Rodrigues  et al.,  2009).  The  cranial  osteosarcoma  features  has  a high  rate  of  metastasis  (Neuwald  et  al.,  2006). Regardless  of  the  therapeutic  protocol  chosen,  the lifetime  is  estimated  at  six  months  to  one  year (Cavalcanti  et  al.,  2004).  The  metastases  signals tend  to  appear  quickly  causing  lethargy,  anorexia, weight  loss  (Gomes  et  al.,  2008).  In  most  cases, euthanasia  is  chosen  for  these  patients  (Daleck  et al., 2006, Gomes et al., 2008, Neuwald et al., 2006). Diagnosis   is   based   on  clinical   history,   physical examination,      radiological      and      scintigraphic findings, and the confirmation made by biopsy and histopathology.    The    cytology    by    fine    needle aspiration can be a form ofdiagnosis in some cases being   a   less   invasive   and   lowest   cost   method
(Oliveira   and   Silveira,   2008).   The   differential diagnosis      includes      other      bone      neoplasia, osteomyelitis,   bone   repair,   bone   diseases   and metabolites    periostitis,    hypertrophic    pulmonary osteoarthropathy,     and      panosteitis      metafisial osteopathy (Souza  et  al.,  2008).  The  clinical  signs of   axial   osteosarcoma   depend   on   the   anatomic development and volume and may cause dysphagia, exophthalmos,  pain  on  opening  the  mouth, facial deformity,  nasal  discharge,  sneezing,  soreness  and signs of neurological disorder (Gomes et al., 2008).
Surgical  treatment  is  not  always  effective  since depending of their location it may becomes difficult to obtain edges free of neoplastic cells, and may be associated  with  chemotherapy and  /  or  radiation therapy (Neuwald et al., 2006). The combination of surgery  with  chemotherapy  has  been  the  treatment protocol  that  provides  improved  survival  (Oliveira and    Silveira,    2008).    The    drug    indicated    for chemotherapy is  the  carboplatin (Rodrigues  et  al., 2009).  Pain  control  is  very  important  for  a  patient having  a neoplasm; it  can  be  administered  as  an analgesic or nonsteroidal anti-inflammatory opioids (Daleck et al., 2009). The objective of this study is to report a osteosarcoma in the axial skeleton case, at the cranial region, in a large sized dog, male, who showed  no metastasis  confronting  some  literature data.

Case report

A   male   White   Shepherd,   8   years   old   was referred   for   evaluation,   diagnosis   and   surgical intervention,  with  a  slight  elevation  in  the  frontal region  of  the  skull,  an  increase  of  3  weeks  (Figure 1A, 1B and 1C). Upon examination, it was observed that  the  patient,  though  having  slight  deformity  of the face showed no clinical signs of involvement of the region of the paranasal sinuses such as sneezing and nasal discharge. It was performed a fine needle aspiration      cytology      (FNAC),      which      was inconclusive.   The   patient   underwent   ultrasound
examination and radiographs of the chest and skull, which  showed  discrete  osteolytic  destruction  in the frontal  bone  of  the  skull,  pulmonary  imaging  with no  markings  and  the  presence  of  anechoic  areas  in the  spleen.  A  surgical  procedure  was  performed  to remove  material  for  histopathological  examination of   the   frontal   region   and   for   splenectomy   and exploratory    laparotomy    for    evaluation    of    the abdominal cavity. The histopathology confirmed the presence  of  osteosarcoma  in  the  frontal  and  nasal bones.    The    patient    then    underwent    surgical resection  of  the  tumor  with  ostectomy  for  border security in the region and curettage of frontal sinus and  choanal  who  presented  with  purulent  sinusitis (Figure  1D).  A  drain  tube  was  placed  in  the nasal cavity for irrigation daily (maintained for 5 days) to avoid  the  formation  of  clots  and  occlusion of  the nasal   conduit.   Anti-inflammatory   and   analgesic drugs were administered for five days after surgery.

The stitches were removed 15 days postoperatively, and the pacient was evaluated by clinical, laboratory and   imaging   examination,   prior   to   the   start   of chemotherapywith  carboplatin.  The  patient  was followed  with  monthly clinical  and radiographic evaluation (Figure 1E and 1F). After four months of surgery,  there  was  a  recurrence  of  the  tumor  that affected    the    orbit    and    adjacent    region.    The evaluation   and   staging   revealed no   signs   of metastasis.  The  dog  was  maintained  on  analgesic and     antiinflammatory     treatment;     associating Dipyrone  (25mg/kg/vo)  every  08  hours,  alternating with  Tramadol  (4mg/kg/vo)  or  morphine  (1.0  mg
/kg/po)     every     08     hours     and     meloxicam (0.1mg/kg/vo) every  24  hours.  The  patient  was euthanized at 10 months after surgery.

Results an Discussion

Osteosarcoma  is  the  most  common  primary bone  cancer  diagnosed  in  dogs  (Neuwald  et  al., 2006),  however,  the  incidence  in  the  axial  skeleton is  25%  (Gomes  et  al.,  2008, Oliveira  and  Silveira, 2008,Cavalcanti  et  al.,  2004),  being  the    female twice  affected  comparedwith  the  occurrence  in males  (Daleck  et  al.,  2006),  and  in  older  dogs  and midsize.  The  patient  reported  was  a  large  dog  and going into the senile age.

The location of the lesion in the frontal region, involving  the  paranasal  sinuses  and  nasal  cavity, corroborates with the literature (Gomes et al., 2008, Rodrigues  et  al.,  2009)  reported  that  the  incidence of 9% of cases with this region.

Initial   clinical   signs   with   increased   frontal region   leading   to   facial   deformityradiographic evidence  of  bone  osteolysis  and  frontal  sinusitis indicated osteosarcoma   (Oliveira   and   Silveira, 2008).    The    sinusitis    is  secondary    to    tumor obstruction   in   the   nasal   cavity   that   prevents drainage of the sinuses to the middle nasal meatus. However,  except  for  the  increase  in  volume,  this patient  had  no  dysphagia,  exophthalmos,  pain  on opening   the   mouth,   nor   signs   of   neurological disorder  (Gomes  et  al.,  2008)  as  reported  in  the literature.    A    fine    needle    aspiration    cytology although  being  a  less  invasive  and  less  expensive exam (Oliveira     and     Silveira,     2008),     was inconclusive   for   this   case,  and   the   patient   was referred for biopsy. The diagnosis was confirmed by the   gold   standard   test   for   cancer,   which   was histopathology  (Gomes  et  al.,  2008,Oliveira  and Silveira, 2008).

Although     the     effectiveness     of     surgical treatment is limited by the location of the tumor, the combination  with  chemotherapy  and/or  radiation (Neuwald  et  al.,  2006)  may  improve  the  prognosis generating   longer   survival   times   (Oliveira   and Silveira,  2008).  This  dog,  15  days  after  surgery, underwent  a  protocol  of carboplatin  (Rodrigues  et al.,   2009)   every   21   days.   Since   he   showed hematological   abnormalities,   the   treatment   was interrupted     after     the     second     session.     This interruption in the chemotherapy protocol may have contributed  to  tumor  recurrence  after  4  months  of surgery,   and   the   patient   was   euthanized at   10
months postoperatively (Daleck et al., 2006, Gomes et al., 2008, Neuwald et al., 2006,5). The euthanasia was   an   owner's   option   because   of   the   tumor extension  into  adjacent  orbit  regions,  making  the surgical procedure not viable.

Pain   control   (Rodrigues   et   al.,   2009)   was satisfactory  in  this  patient  with  the  combination  of ananalgesic   (dipyrone),   an   opioid   (tramadol   / morphine)  and  an  anti-inflammatory  (Meloxicam). This outcome was measured by daily observation of feed,  activities,  interaction  with  the  owner,  and physiological   signals.   Until   the   euthanasia,   the patient   was   orexigenic   with   normodipsia   and normuria.

However,  usually  patients  with  axial  skeleton tumor  classified  as  cranial  osteosarcoma  have  a  high rate of metastasis (Neuwald et al., 2006), a fact that  was  not  observed  during  follow-up  of  this patient,  even  with the  same  tumor  recurrence,  the patient continued to feed and daily activities with no clinical  signs  of  lethargy,  anorexia,  weight  loss (Gomes  et  al.,  2008).  The  patient  was  monthly evaluated  with  chest  radiography  and  abdominal ultrasonography, and was not observed evolution of possible  outbreaks  of  micrometastases,  which  are
reported as common in patients with osteosarcoma.

Conclusion

The  axial  skeleton  osteosarcoma  is  a  locally invasive  neoplasm  and  very  little  metastatic,  as reported  in  this  case.  The  prognosis  is  guarded  to grave,  with  frequent  euthanasia  in  patients  with recurrences  due  to  the  extension  of  the  neoplastic lesion.

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