Neoplasia of the Axial Skeleton

Chapter 101 Neoplasia of the Axial Skeleton



Mark M. Smith



ETIOLOGY


Osteosarcoma and chondrosarcoma are the two most common primary neoplasms affecting the axial skeleton. These neoplasms have a similar radiographic appearance, with osteolytic, osteoblastic, or mixed osteoblastic/osteolytic characteristics. Hemangiosarcoma and fibrosarcoma are other primary bone tumors that must be considered. Overall, these tumors more commonly affect the ribs and pelvis than the vertebrae. Multilobular osteoma (chondroma rodens) is the most common tumor of the skull.


Early recognition and accurate diagnosis are of paramount importance for client education and rationale for surgical intervention. Surgery may be diagnostic (vertebrae), palliative (pelvis), or curative (rib), depending on tumor invasiveness and location of axial skeletal involvement. Tumors of the mandible, maxilla, and nasal cavity are discussed in other chapters in this section. The types of neoplasms and principles of treatment discussed in this chapter are similar to those for tumors of the cranium. Removal of cranial tumors requires specialized equipment and skills and therefore is best handled by a surgical specialist. Tumors of the appendicular skeleton are discussed in Chapter 116.



CLINICAL SIGNS



• Patients usually are presented for swelling over a bony prominence.

• Intrathoracic extension of neoplasia of the rib may cause respiratory compromise.

• Pain or an unusual gait secondary to neurologic dysfunction (transverse myelopathy) may be related to neoplasms of the vertebrae.

• Animals with skull tumors usually are presented because of a palpable mass. Neurologic signs may develop if brain impingement occurs.

• Constipation may result from pelvic tumors.


DIAGNOSIS



Pelvis and Ribs



• Include two radiographic projections of the lesion.

• Radiographic signs of primary bone neoplasms (e.g., osteosarcoma, chondrosarcoma) may range from primarily lytic to proliferative lesions.

• Polyostotic lytic lesions are seen with malignant lymphoma and multiple myeloma (see Chapter 27).



Key Point


Do not use radiography as the sole basis for determining tumor type.



• Determine if metastatic disease is present.

• Perform palpation and fine-needle aspiration of enlarged regional lymph nodes.

• Perform abdominal palpation for mass lesions, vertebral palpation for metastasis-related pain, and a rectal examination for intrapelvic masses.

• Evaluate three-projection thoracic radiographs (ventrodorsal, left, and right lateral) to detect pulmonary metastasis.


Skull and Vertebrae



• Survey radiographs of the spine often show osteolysis secondary to primary bone neoplasia or to invasion of soft tissue neoplasia.

• Osteosarcoma or multilobular osteoma of the cranium appears radiographically as a proliferative bony lesion of the flat bones.

• Perform cerebrospinal fluid (CSF) analysis to rule out infection and inflammation (see Chapter 125). CSF of patients with vertebral neoplasia may have increased levels of protein and elevated pressure.



Key Point


Because most tumors affecting the spinal cord are extradural, cytologic examination of the CSF may be normal.



• Myelography and computed tomography (CT) are important to detect the exact site of the vertebral tumor and the extent of spinal cord compression (see Chapter 128).



Key Point


Metastatic lesions from remote malignant tumors may mimic primary neoplasms of the axial skeleton. Histopathologic examination of biopsy tissue is required for differentiation.



• CT or magnetic resonance imaging (MRI) is useful to evaluate intracranial effects of skull tumors (see Chapter 126).


Bone Biopsy



Objectives



• Obtain multiple tissue samples of the tumor for histopathologic diagnosis.

• Avoid causing iatrogenic trauma to the vertebrae or skull, if they are involved.


Equipment



• Small suture pack and suture material

• Jamshidi-type biopsy needle or bone trephine

• Sterile ruler


Technique



1. Prepare the cutaneous area over the tumor site for aseptic surgery.

2. Make a skin incision large enough to introduce the biopsy instrument over the center of the lesion.

3. Measure the center of the tumor from the nearest prominent anatomic landmark.

4. Take a minimum of two biopsies: one from the center of the tumor and one from the center directed to the periphery. Use extreme caution when performing biopsy of tumors of the cranium.

5. Using a horizontal mattress pattern, place sutures of absorbable material in the subcutaneous or fascial layers to minimize hemorrhage from the biopsy site.

6. Close the skin with non-absorbable suture material in a simple interrupted pattern.



Key Point


Biopsy of vertebral lesions is best performed during decompressive laminectomy or with the aid of fluoroscopy to guide biopsy needle placement.



TREATMENT



Surgical Procedures for Rib Neoplasia: Resection and Thoracic Wall Reconstruction



Objectives



• Completely remove the thoracic wall mass.

• Attempt to obtain wide tumor-free margins.

• Minimize hemorrhage.

• Provide rigid reconstruction to prevent abnormal chest wall movement.

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  4. Otitis Media and Otitis Interna

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Neoplasia of the Axial Skeleton

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