+ Biologic Behavior

  • Primary rib tumors are uncommon and are usually malignant and metastatic
  • OSA is the most common rib tumor in dogs and accounts for 73% of all rib tumors
  • Rib OSA had a similar biologic behaviour to appendicular OSA
  • Other malignant rib tumors include CSA, FSA, MCT, and HSA
  • Malignant rib tumors invade the thoracic wall and can have extensive intrathoracic expansion
  • 27%-45% metastatic rate for rib OSA with metastasis to the lungs very common
  • Telangiectatic OSA of the rib is associated with the highest rate of metastasis
  • Benign rib tumors include infiltrative lipomas and calcinosis circumscripta

+ Signalment

  • No sex or breed predisposition
  • Large dogs (> 20 kg) over-represented
  • Median age 4.5-5.5 years for dogs with OSA and 6 years for dogs with CSA

+ Clinical Signs

  • Firm and fixed thoracic wall mass
  • Non-specific signs: pain, weight loss, lethargy, lameness, and dyspnea

+ Diagnosis

  • Primary and metastatic rub tumors may produce lytic, sclerotic, or mixed radiographic patterns
  • Primary rib tumors occur in the distal 3rd of rib and usually at the costochondral junction
  • Radiographic features are unable differentiate OSA from CSA
  • Other radiographic findings: displacement of adjacent ribs and medial displacement of parietal pleura producing extrapleural sign and displacement of intrathoracic structures such as heart and lungs
  • Biopsy recommended

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+ Treatment

  • 3 classifications of hemipelvectomy: radical, conservative, and internal
  • Radical: limb amputation with separation of pelvis through sacroiliac joint
  • Conservative: limb amputation with preservation of sacroiliac joint and cranial ilium
  • Internal: preservation of limb
  • Musculocutaneous flaps are preferred for wound closure although fasciocutaneous flaps acceptable
  • Medial extent of the tumor is the most difficult dissection with midline (sacrum or pubis) the surgical limit
  • Complications are rare and similar to limb amputation
  • Complications in humans include infection, skin flap necrosis, herniation, fecal and urinary incontinence if pudendal nerve roots transected, thromboembolic disease, and local tumor recurrence

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+ Prognosis

  • MST 120 days for OSA following chest wall resection, with 6-month survival rate 20%
  • MST 240 days for OSA following chest wall resection and chemotherapy is 240 days
  • MST 299-1,080 days for CSA
  • Survival times range from 120-450 days for dogs with FSA
  • Survival times range from 30-150 days for dogs with HSA
  • Prognostic factors: tumor type and complete histologic resection
  • Local tumor recurrence ± metastasis is 5.6-times more likely with incomplete resection