Scapular tumors: A case report and review of the literature

Scapular tumors are most commonly treated with full forelimb amputation, not necessarily because it is needed to obtain complete margins but because this procedure is the more common practice and patients typically do very well with it.   In many of these patients though, a forequarter amputation may be more extensive than is required for complete excision and in other patients, surgery may not be pursued if an amputation is thought to be the needed procedure and the patient is deemed not to be a good amputation candidate or the owner does not want a tripod dog.  Therefore, being aware of scapulectomy, including the indications and outcome, is not only important for veterinarians that perform the procedure, but all veterinarians because otherwise, if the initial veterinarian evaluating the patient is not educated on the procedure there is a subset of owners that will never pursue referral for their pet with a scapular tumor.

At Hope Veterinary Specialists, Nox, a 3 yo MC German Shorthair Pointer presented to the surgery service for evaluation of an acute onset left thoracic limb lameness.  He developed the lameness after he had a collision with his housemate. On physical examination, he was painful on manipulation of the left shoulder. Radiographs were performed and the official radiology report showed no abnormalities or cause for the lameness.  Rest was recommended and Rimadyl was prescribed.  Nox initially improved but then his lameness acutely worsened.  Thirteen days later, on repeat physical examination, there was a firm swelling along the caudodorsal aspect of the left scapula, which was painful.  Repeat radiographs were performed which in the craniocaudal view showed osseous remodeling and periosteal reaction or proliferation associated with the dorsal scapula and along the lateral and medial margins and soft tissue thickening focally over the lateral dorsal margin of the scapula (Figure 1).

Scapular tumors are most commonly diagnosed in middle to old age large breed dogs.  Nox’s presenting clinical sign of lameness and a swelling noted along the scapula on physical examination are both common occurrences for patients with a primary scapular tumor.  In one study, 86% of dogs with scapular tumors were lame, 33% had a scapular mass or swelling and 19% had both.

Orthogonal radiograph views of the scapula as performed in Nox, are recommended to assist in the diagnosis of a scapular tumor. Radiographic changes that are commonly seen are osteolytic and osteoproliferative changes, as noted with primary bone tumors in other locations.  It can be more difficult though to see these changes in the scapula than in other bones due to the overlap of the thorax and spine.

If a scapular mass is noted, in addition to radiographs of the lesion, three-view thoracic radiographs to access for metastatic disease are important, as most scapular tumors are malignant, with many having a high risk of metastatic spread to the lungs.  Most cases though have no evidence of spread at the time of diagnosis.   In one study, only 5.4% had metastatic disease to the lungs on initial thoracic radiographs.  In addition to scapular and thoracic radiographs, abdominal ultrasound can be performed for staging.  This can be extremely important with certain types of bone tumors such as hemangiosarcoma or histolytic sarcoma.

Preoperatively a fine needle aspirate or incisional biopsy can be performed to try to obtain a definitive diagnosis.  This becomes important if the prognosis is going to affect if the owner wants to pursue surgery because most scapular tumors are malignant and surgery is the first treatment of choice regardless of the definitive diagnosis.  As with other locations, a FNA has the benefit of decreased risk of complications, decreased cost and faster results.  Ultrasound guidance can be helpful for a FNA of a bone lesion because it can be used to guide the needle into a section of bone that appears lytic increasing the likely penetration of the needle into the bone.  In one study, 11 cases of scapular neoplasia had a preoperative FNA and in all cases, the results were consistent with the finalized histopathology.

When performing a bone biopsy of a scapular lesion, the same principles apply as when collecting a sample from other bones.   The biopsy should be collected from the center of the lesion and the biopsy tract positioned so that it can be easily resected at the time of definitive surgery.  Bone biopsies can be collected using an open surgical technique, Michelle trephine or  Jamshidi needle biopsy.  The open procedure has the advantages of a larger sample but increased risk of complications due to a larger procedure.  A Michelle trephine and Jamshidi needle biopsy are performed by a closed approach with a Michelle trephine collecting a larger sample and therefore having an increased risk of causing a fracture.  It is reported that a Michelle trephine and Jamshidi needle biopsy can have an accurate diagnosis in greater than 80% of cases (93.8% diagnostic accuracy rate for Michelle trephine and 91.9% accuracy of diagnosis of neoplasia vs. other and 82.3% accuracy for tumor type for Jamshidi needle biopsy).

In Nox,  a bone biopsy with submission for histopathology was performed which was interpreted by the pathologist as sarcoma, suspicious for hemangiosarcoma. Three-view thoracic radiographs, blood work, and abdominal ultrasound were performed which had no significant findings.

A CT scan is extremely helpful in determining the full extent of the disease in scapular masses and greatly assists in surgically planning.  After staging diagnostics, a CT scan was performed in Nox.  In addition to obtaining a CT of the affected scapula, the entire thoracic was imaged which is important because a CT scan is able to identify smaller metastatic lesions to the lungs than radiographs.    Radiographs can identify lesions as small as 7-9 mm while CT can identify lesions as small as 1 mm. Nox’s CT scan was interpreted as showing a large monostotic osteolytic mass arising from the caudoventral aspect of the left scapula, resulting in the expansile destruction of the scapular cortices and swelling of the surrounding soft tissues.  The mass was of mixed soft tissue and mineral attenuation, measuring ~3.5 x 5.9 x 7.3 cm with an irregular periosteal reaction extending along the medial and lateral surfaces of the scapula (Figure 2).

Following the CT scan, a scapulectomy was recommended for Nox.  Scapular tumors should be removed with 3 cm margins and they can be removed via a partial scapulectomy, subtotal scapulectomy or total scapulectomy.  In Nox, to remove the lesion with 3 cm margins, a subtotal scapulectomy was recommended which is defined as greater than or equal to 75% resection of the scapula leaving the glenoid of the scapula.  A partial scapulectomy is the removal of < 75% of the scapula and total scapulectomy is resection of the entire scapula.   Postoperatively, all resected tissue should be submitted for histopathology regardless of if a bone biopsy was performed, to confirm the diagnosis.

Nox’s surgery went well and approximately 80% of the scapula was resected as well as the biopsy tract (Figure 3).  Finalized histopathology for Nox revealed hemangiosarcoma grade II with complete margins.  Hemangiosarcoma is reported in other patients with scapular neoplasia but is not the most common diagnosis. Osteosarcoma is by far the most common primary tumor of the scapula in dogs (reported as 63.3-75% of scapular tumors in dogs).  In addition to osteosarcoma, soft tissue sarcoma, chondrosarcoma and hemangiosarcoma are reported followed by rare reports of liposarcoma, histiocytic sarcoma, and skeletal angiomatosis.

In general with scapulectomy, limb use is often thought to be good to excellent with partial/subtotal scapulectomy but potentially less predictable with total scapulectomy.  In the published paper with the largest number of reported dogs with a scapulectomy, limb use was reported to range from fair to excellent in most dogs.  Mostly commonly within the initial postoperative period use was poor to fair (36.5 % poor, 41.5% fair, 29.3% good and 4.9% excellent) and most had improved to fair to good by 1 month (19.5% poor, 41.5% fair, 29.3% good and 9.8% excellent).  Limb use at 3 months postoperatively was only recorded for 14/41dogs and 3 months postoperatively for 6/41 dogs making the in-depth discussion more difficult.  With longer-term assessment though, it was able to be reported that 50% that had poor use and 58.8% that had fair use at 1 month had further improvement.  Important to note also is that this study found no correlation between percent of the scapula removal and limb use at 14 days and 1 month.

In Nox at 1 day postoperatively, he was non-weight bearing to toe touching lame and was reported to still be mostly non-weightbearing on the limb at 12 days post surgery. At 26 days postoperatively, he was reported to still be mostly non-weightbearing but would place the paw on the floor and did not seem painful.  At 68 days postoperatively on physical examination he was reported to be partially weight bearing lame on his limb.  A video provided by the owner shows Nox running at 8 weeks and 11 weeks post surgery and he has good use of the limb with occasional non-weightbearing steps (video 1 and 2).

The prognosis for scapular tumors, as with primary bone tumors, is dependant on the type of neoplasia.   Osteosarcoma is reported to behave similar to appendicular osteosarcoma with a high rate of metastatic spread and therefore chemotherapy is recommended.  In general, osteosarcoma and hemangiosarcoma have reported survival times of usually less than 12 months and chondrosarcoma greater than 2 years.  In one study the median survival time was 246 days with osteosarcoma, 413 days for soft tissue sarcoma and was not reached for chondrosarcoma.

In conclusion, a scapulectomy is often a good treatment choice for patients with scapular tumors and should be considered instead of an amputation in many of these cases.  Post scapulectomy, dogs frequently have fair to excellent use of the limb and are not painful but the most common tumor type is osteosarcoma, which has a high rate of metastatic spread and therefore owners need to know that depending on the type of tumor, scapulectomy is often not curative.

Figure 1: Craniocaudal view showing osseous remodeling and periosteal reaction or proliferation associated with the dorsal scapula and along the lateral and medial margins of the scapula and soft tissue thickening focally over the lateral dorsal margin of the scapula.  No changes of the scapula noted on the lateral view.

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Figure 1 lat 

Figure 2: CT scan showing a large monostotic osteolytic mass arising from the caudoventral aspect of the left scapula, resulting in the expansile destruction of the scapular cortices and swelling of the surrounding soft tissues. 

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References

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Dernell WS. Tumours of the skeletal system. In: Dobson JM. Lascelles BDX, eds. BSAVA Manual of Canine and Feline Oncology. Gloucester: BSAVA, 2011;159-177.

Dernell WS, Ehrhart NP, et al. Tumors of the skeletal system. In: Withrow SJ, Vail DM, eds. Withrow & MacEwen’s Small Animal Clinical Oncology. St Louis, Missouri: Elsevier Saunders, 2007; 540-582.

Kirpensteijn J, Straw RC, Pardo AD, et al: Partial and total scapulectomy in the dog. J Am Anim Hosp Assoc 1994;30:313. http://agris.fao.org/agris-search/search.do?recordID=US9512988

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Liptak JM, Dernell WS, et al. Musculoskeletal system. In: Kudnig ST, Sequin B, eds. Veterinary Surgical Oncology. UK: Wiley-Blackwell, 2012;491-568.

Montinaro V, Boston SE, et al. Clinical outcome of 42 dogs with scapular tumors treated by scapulectomy: a Veterinary Society of Surgical Oncology (VSSO) retrospective study (1995-2010). Vet Surg 2013;42(1):943-50. http://onlinelibrary.wiley.com/doi/10.1111/j.1532-950X.2013.12066.x/full

Nemanic S, London CA. Comparison of thoracic radiographs and single breath-hold helical CT for detection of pulmonary nodules in dogs with metastatic neoplasia. J Vet Intern Med 2006;20(3):508-15. http://onlinelibrary.wiley.com/doi/10.1111/j.1939-1676.2006.tb02889.x/full

Peck J. Scapula. In: Tobias KM, Johnston SA, eds. Veterinary Surgery Small Animal. St. Louis, Missouri: Elsevier Saunders, 2012;685-708. 

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