Biologic Behaviour

•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

Treatment

•en bloc excision with chest wall reconstruction

•chest wall can be reconstructed with latissimus dorsi muscle flap, external abdominal oblique muscle flap, diaphragmatic advancement, and prosthetic mesh depending on the size and location of the defect

•caudal lung lobectomy may be required to permit adequate closure

•chemotherapy is recommended for dogs with rib OSA

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