Neoplasia of Thoracic and Pelvic Limbs

Chapter 116 Neoplasia of Thoracic and Pelvic Limbs



Matthew Palmisano, Milan Milovancev


Tumors of the appendicular skeleton can occur either as a primary or metastatic lesion. Primary bone tumors occur most commonly in middle-aged and older animals. However, younger dogs 18 to 24 months of age can be affected.




Key Point


Primary bone neoplasms are usually metaphyseal in location, involve one bone, and usually do not cross a joint space.


Metastatic bone tumors may occur anywhere along the bone, and can affect multiple bones. Metastatic lesions can occur with any tumor type, but tumors of epithelial origin are more commonly seen to metastasize to bone.



Etiology




Primary Skeletal Neoplasms



Osteosarcoma




Key Point


Osteosarcoma (OSA) accounts for approximately 85% of all primary bone tumors in dogs.



• 75% of OSA occurs in the appendicular skeleton.

• OSA is usually an aggressive lesion originating in the metaphysis of long bones.

• The distal radius is the most common site for OSA, making up 40% of all skeletal OSA. Other common sites include the proximal humerus, distal femur, and proximal tibia.

• OSA is a biologically aggressive neoplasm, with a doubling time of 21 days.

• Although 80% to 90% of dogs lack radiographic evidence of pulmonary metastases at time of diagnosis, most dogs are euthanized due to complications associated with metastatic lung disease.

• Large- and giant-breed dogs are over-represented in most studies. Only 5% of OSA occurs in dogs weighing less than 15 kg.

• One study found that OSA in small-breed dogs behaves differently than in their large-breed counterparts, representing less than 50% of all skeletal neoplasms and with no apparent predilection for the distal radius. The proximal humerus is the most common site in the small-breed dog.

• Appendicular OSA in cats behaves less aggressively than canine OSA, with affected cats surviving a mean of 14.8 months following amputation. The hind limb is more commonly affected in the cat.

• Cisplatin, carboplatin, and doxorubicin are chemotherapeutic agents frequently used in treatment of OSA. Survival rates reported with chemotherapy are 45% survival to 1 year, and 30% 2-year survival.

• Poor prognostic indicators in dogs with OSA include a preoperative alkaline phosphatase level greater than 110 U/L, OSA in young patients, high tumor grade, and radiographic evidence of pulmonary metastases.

• Long-term prognosis is poor. Survival rates in dogs diagnosed with OSA are 10% survival at 1 year without chemotherapy. Amputation will achieve local tumor control and relief from pain, but the procedure does not extend long-term life span.


Chondrosarcoma



• Chondrosarcoma represents 5% to 10% of primary tumors of the appendicular skeleton.

• Medium- to large-breed dogs are most commonly affected.

• Unlike OSA, surgical resection of chondrosarcoma is associated with an increased long-term survival when compared to non-surgical management.

• However, long-term prognosis is still guarded, with a 30% 1-year survival seen with treatment.

Fibrosarcoma and hemangiosarcoma are the third and fourth most frequently seen primary tumors of bone, respectively. Both tumors together comprise slightly less than 5% of primary tumors of bone.


See Table 116-1 for biologic behavior, treatment, and prognosis of the most common canine malignant appendicular skeletal tumors.



Table 116-1 COMMON CANINE MALIGNANT APPENDICULAR SKELETAL TUMORS

image


Other Primary Skeletal Neoplasms


Other rare bone tumors include osteoma, chondroma, osteochondroma, enchondroma, malignant mesenchymoma, liposarcoma, plasma cell myeloma, lymphosarcoma, and giant cell tumor.



Primary Soft Tissue Neoplasms



Synovial Cell Sarcoma



• Synovial cell sarcomas are tumors that arise from the joint capsule.

• Most commonly seen in middle-aged to older animals.

• The stifle and elbow joint are affected in nearly 75% of cases.

• Radiographs reveal an osteolytic pattern associated with a joint. Classically, this tumor crosses the joint space. This differs from primary tumors of bone, which characteristically do not cross the joint space.

• Histologic grading carries prognostic significance, as tumors with higher biologic grading are more likely to metastasize. The metastatic rate varies from 20% to 70%, depending on histologic grading.

• Recurrence is common after local surgical resection. Therefore, limb amputation is recommended for local tumor control.


Other Primary Soft Tissue Neoplasms


Other primary soft tissue appendicular tumors include hemangiosarcoma, rhabdomyosarcoma, lymphosarcoma, fibrosarcoma, and malignant histiocytosis. These tumors are rarely seen and require histologic analysis for diagnosis and prognosis. Since sarcomas do not exfoliate easily, fine-needle aspiration is generally unrewarding. Therefore, incisional or excisional biopsies are required for diagnosis.



Metastatic Neoplasia



• Metastasis to bone from primary neoplasms located elsewhere in the body is occasionally seen.

• Any neoplasm may metastasize to bone, but carcinomas are more likely to metastasize to bone than sarcomas. In particular, urogenital neoplasms such as prostatic carcinoma, transitional cell carcinoma of the bladder, and mammary carcinomas tend to metastasize to bone.



Key Point


Tumors that metastasize to bone are usually seen in the diaphysis, whereas primary tumors of bone are usually metaphyseal in location.



• A thorough diagnostic workup (bloodwork, three-view chest radiography, abdominal ultrasonography) is essential to determine the primary source of neoplasia.

• Biopsy of both the primary mass and bone lesion is important for accurate diagnosis and staging of disease.


Clinical Signs



• Clinical signs are variable and range from a subtle lameness and non-painful swelling to a non–weight bearing lameness with obvious limb deformation.

• Occasionally, acute lameness will be seen secondary to pathologic fracture through the diseased bone.

• Rarely, dogs will have respiratory signs at presentation due to metastatic pulmonary disease.


Diagnosis



• A presumptive diagnosis is usually made based on signalment, history, physical examination, and radiographic findings.

• A thorough physical examination, complete blood count, serum biochemical profile, and urinalysis are important to assess the patient’s overall health status and check for concurrent conditions that may affect treatment options.



Diagnostic Imaging



• Obtain a three-view thoracic radiographic study (i.e., right lateral, left lateral, and ventrodorsal or dorsoventral views) to evaluate the patient for pulmonary metastasis.

• Chest radiography and nuclear imaging are two modalities that, when used together, detect metastasis in about 18% of cases. Availability of nuclear imaging is limited in private practice.

• Other advanced imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), are useful in locating metastasis to lung and other extra-skeletal sites. Use of imaging to estimate tumor margins is important in limb-sparing surgeries and in radiation therapy planning.

• Radiographic patterns of both primary and secondary bony neoplasia are very similar, with a combined osteolytic-osteoproliferative pattern seen. Aggressive radiographic features such as cortical lysis, periosteal reaction, and bony proliferation strongly support neoplasia.


Biopsy



• Definitive diagnosis requires representative biopsy performed either using a bone core biopsy (Jamshidi needle, Michel trephine, or open-incisional) in the radiographic middle of the lesion or a wedge biopsy if the mass is soft tissue in origin (Fig. 116-1).

• Jamshidi needle biopsy has an accuracy rate of 91.9% for detection of tumor versus other disease processes and 82.3% for diagnosis of exact tumor type.

• Perform a fine needle aspirate on all enlarged lymph nodes and evaluate cytologically for metastasis.

image

Figure 116-1 A, Biopsy of bone by closed technique with a Jamshidi needle. B, With the stylet locked in place, advance the cannula through soft tissue until bone is reached. C, Remove the stylet and penetrate the one cortex with the cannula. Withdraw the cannula and repeat the procedure with redirection of the needle.



Treatment



• Treatment recommendations depend on tumor type and location.



Surgery



• Although some small or benign tumors may be treated by local resection, most appendicular neoplasms require complete or partial amputation of the affected limb, primarily for palliation of pain (see discussion of amputation later in this chapter). Evaluate the patient’s other limbs to ensure that adequate function can be carried out with the remaining three limbs.



Key Point


Limb amputation is contraindicated in patients that will have difficulty ambulating with three limbs. This includes overweight and obese patients or patients that have significant orthopedic disease in the other three limbs that will affect postoperative ambulation.



• Some giant-breed dogs have difficulty ambulating initially following amputation due to their large size and require some assistance postoperatively. Most of these patients adjust quickly.

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Neoplasia of Thoracic and Pelvic Limbs

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