• View in gallery
    Figure 1

    Clinical gross image of the right eye ([oculus dextrus (OD); A] and left eye [oculus sinister (OS); B] of an 11-year-old spayed female pit bull–type mixed-breed dog. A—There is elevation of the third eyelid (asterisk), enophthalmos, anterior uveitis with a dyscoric pupil due to posterior synechiae (arrow), and an immature cataract OD. B—There is a small, vascularized mass (arrow) on the anterior portion of the third eyelid OS. No other abnormal findings to OS could be appreciated.

  • View in gallery
    Figure 2

    Photomicrographs of ultrasound-guided fine-needle aspirate samples of an OD orbital mass of the dog described in Figure 1 showing eosinophilic product (arrows) within cells and extracellularly (potential osteoid), cells with abundant rounded to wispy to spindle-shaped basophilic cytoplasm, large ovoid nuclei with stippled chromatin, large prominent nucleoli, moderate anisocytosis and anisokaryosis, and rare binucleate cells. A and B—Modified Romanowsky stain; bar = 20 µm and 10 µm, respectively. C and D—Wright-Giemsa stain; bar = 20 µm and 10 µm, respectively. E and F—Wright-Giemsa stain followed by a 1-hour incubation with nitroblue tetrazolium chloride/5-bromo-4-chloro-3-indoyl phosphate toluidine salt substrate (this substrate is converted by alkaline phosphatase to stain cells that produce alkaline phosphatase black.); bar = 20 µm and 10 µm, respectively.

  • View in gallery
    Figure 3

    Photomicrographs of tissue sections from an OD orbital mass removed from the dog described in Figure 1. A—Repeating nodular pattern (asterisks) with mineralized bone (arrows) in the center of each nodule. Bland spindle cells (star) surround the mineralized bone. H&E stain; bar = 200 µm. B—Higher magnification showing the same nodular pattern (asterisk), with mineralized bone (arrows) surrounded by spindle cells (star). H&E stain; bar = 100 µm.

  • 1.

    Maggs DJ. The ophthalmic examination and diagnostic testing. In: Maggs DJ, Miller PE, Ofri R, eds. Slatter’s Fundamental of Veterinary Ophthalmology. 6th ed. St. Louis, MO: Saunders Elsevier; 2018:1850.

    • Search Google Scholar
    • Export Citation
  • 2.

    Barger A, Graca R, Bailey K, et al. Use of alkaline phosphatase staining to differentiate canine osteosarcoma from other vimentin-positive tumors. Vet Pathol. 2005;42(2):161165.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Ramsey DT, Marretta SM, Hamor RE, et al. Ophthalmic manifestations and complications of dental disease in dogs and cats. J Am Anim Hosp Assoc. 1996;32:215224.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Holscher MA, Netsky MG, Lee TT, et al. Granular cell myoblastoma (schwannoma) in the orbit and cerebrum of two dogs. Canine Pract. 1983;10:3538.

    • Search Google Scholar
    • Export Citation
  • 5.

    Kitagawa M, Okada M, Watari T, Sato T, Kanayama K, Sakai T. Ocular granulomatous meningoencephalomyelitis in a dog: magnetic resonance images and clinical findings. J. Vet. Med. Sci. 2009;71:233237.

    • Search Google Scholar
    • Export Citation
  • 6.

    Collinson PN, Peiffer RL. Clinical presentation, morphology and behavior of primary choroidal melanomas in eight dogs. Prog Comp Vet Ophthalmol. 1993;3:158164.

    • Search Google Scholar
    • Export Citation
  • 7.

    Voges AK, Ackerman N. Magnetic resonance evaluation of intra and extracranial extension of nasal adenocarcinoma in a dog and cat. Vet Radiol Ultrasound. 1995;36:196200.

    • Search Google Scholar
    • Export Citation
  • 8.

    Burk RL. Computer tomographic imaging of nasal disease in 100 dogs. Vet Radiol Ultrasound. 1992;33:177180.

  • 9.

    Dennis R, Barnett KC, Sansom J, et al. Unilateral exophthalmos and strabismus due to cranio-mandibular osteopathy. J Small Anim Pract. 1993;34:457461.

    • Search Google Scholar
    • Export Citation
  • 10.

    Ofri R. Neuroophthalmic diseases. In: Maggs DJ, Miller PE, Ofri R, eds. Slatter’s Fundamental of Veterinary Ophthalmology. 6th ed. St. Louis, MO: Saunders Elsevier; 2018:390431.

    • Search Google Scholar
    • Export Citation
  • 11.

    Pool RR. Tumors of bone and cartilage. In: Moulton JE, ed. Tumors of Domestic Animals. 3rd ed. Berkeley, CA: University of California Press; 1990:157230.

    • Search Google Scholar
    • Export Citation
  • 12.

    Diamond SS, Raflo CP, Anderson MP. Multilobular osteosarcoma in the dog. Vet Pathol. 1980;17:759763.

  • 13.

    Losco PE, Diters RW, Walsii KM. Canine multilobular osteosarcoma of the skull with metastasis. J Comp Pathol. 1984;94:621624.

  • 14.

    McCalla TL, Moore CP, Turk J, Collier LL, Pope ER. Multilobular osteosarcoma of the mandible and orbit in a dog. Vet Pathol. 1989;26(1):9294.

    • Search Google Scholar
    • Export Citation
  • 15.

    Rühli MB, Spiess BM. Retrobulbar space-occupying lesions in dogs and cats: symptoms and diagnosis. Tierarztl Prax. 1995;23:306312.

  • 16.

    Mason DR, Lamb CR, McLellan GJ. Ultrasonographic findings in 50 dogs with retrobulbar disease. J Am Anim Hosp Assoc. 2001;37(6):557562.

  • 17.

    Hendrix DVH, Gelatt KN. Diagnosis, treatment and outcome of orbital neoplasia in dogs: a retrospective study of 44 cases. J Small Anim Pract. 2000;41:105108.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18.

    Cook CS. Diseases of the orbit. In: Morgan RV, ed. Handbook of Small Animal Practice. 3rd ed. Philadelphia, PA: Saunders; 1997:10761084.

    • Search Google Scholar
    • Export Citation
  • 19.

    Spiess M, Wallin H, Kanson N. Diseases of the canine orbit. In: Gelatt KN, ed. Verterinary Ophthalmolog. 3rd ed. Philadelphia, PA: Lipponcott, Williams, and Wilkins; 1997:511533.

    • Search Google Scholar
    • Export Citation
  • 20.

    Dernell WS, Straw RC, Cooper MF, Powers BE, LaRue SM, Withrow SJ. Multilobular osteochondrosarcoma in 39 dogs: 1979–1993. J Am Anim Hosp Assoc. 1998;34(1):1118.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21.

    Straw RC, LeCouteur RA, Powers BE, Withrow SJ. Multilobular osteochondrosarcoma of the canine skull: 16 cases (1978–1988). J Am Vet Med Assoc. 1989;195:17641769.

    • PubMed
    • Search Google Scholar
    • Export Citation

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Abstract

In collaboration with the American College of Veterinary Pathologists

Abstract

In collaboration with the American College of Veterinary Pathologists

History

An 11-year-old spayed female pit bull–type mixed-breed dog was presented to the Ophthalmology service at Colorado State University’s Veterinary Teaching Hospital (CSU-VTH) for an evaluation of bilaterally elevated third eyelids with a nodule on the left third eyelid. The referring veterinarian had suspected Horner syndrome as a differential diagnosis due to the more pronounced elevated right third eyelid, enophthalmos, and miotic pupil in the right eye (oculus dextrus [OD]) compared with the left eye (oculus sinister [OS]). The clinical signs were first noticed about a month prior to when the dog was presented to the CSU-VTH.

Clinical and Gross Findings

Findings on physical examination were consistent with chronic osteoarthritis and allergies but otherwise unremarkable. On the initial ophthalmic examination, the neuro-ophthalmic examination (including menace response, dazzle reflex, palpebral reflex, as well as direct and indirect pupillary light reflexes) findings were unremarkable for both eyes (OU). Results for diagnostic tests and ophthalmic examination, which consisted of Schirmer tear testing, intraocular pressure (IOP) measurement, fluorescein staining, slitlamp biomicroscope examination, and indirect ophthalmoscopy OU, were all within reference limits.1

Ophthalmic examination OD revealed moderate elevation and hyperemia of the third eyelid and enophthalmos of the globe. The cornea was clear, and there was 2+ flare in the anterior chamber (flare scale; trace to 4+), a dyscoric (ovoid) pupil due to posterior synechiae, and a thickened iris. The lens had dense nuclear sclerosis and an immature cataract (Figure 1). The posterior segment could not be visualized OD due to third eyelid elevation and lens opacity.

Figure 1
Figure 1

Clinical gross image of the right eye ([oculus dextrus (OD); A] and left eye [oculus sinister (OS); B] of an 11-year-old spayed female pit bull–type mixed-breed dog. A—There is elevation of the third eyelid (asterisk), enophthalmos, anterior uveitis with a dyscoric pupil due to posterior synechiae (arrow), and an immature cataract OD. B—There is a small, vascularized mass (arrow) on the anterior portion of the third eyelid OS. No other abnormal findings to OS could be appreciated.

Citation: Journal of the American Veterinary Medical Association 259, S2; 10.2460/javma.20.03.0155

Ophthalmic examination OS revealed a focal (2 X 3 mm) minimally raised hyperemic mass located on the anterior surface of the third eyelid OS. The globe was otherwise clinically normal except for age-related nuclear sclerosis and iris atrophy (Figure 1). The dog was started on medical management for anterior uveitis OD with topical prednisolone acetate 1% ophthalmic suspension (Sandoz Inc) and atropine 1% ophthalmic solution (Akorn Inc).

At the 2-week recheck examination, the owner reported that the dog had increased ocular discharge and swelling OD over the past 2 days. Findings on neuro-ophthalmic examination OU were within reference limits except for an absent direct pupillary light reflex OD due to posterior synechiae restricting pupil mobility. Ophthalmic examination OD revealed worsening enophthalmos with severe third eyelid elevation and displacement of the third eyelid away from the globe. Clinical signs prompted palpation of the third eyelid. The palpation revealed a firm soft tissue mass ventromedial to the gland of the third eyelid located beneath the conjunctiva with attachment to the medial orbital rim. The anterior uveitis had resolved indicating adequate control with medical management, but chronic posterior synechiae had caused adhesions that made the pupil unable to constrict to light. The remaining findings from the examinations OU were static to previous examinations. Following diagnosis of a suspected orbital mass, CT was discussed but declined by the owner due to financial restraints. Thoracic radiography, ocular ultrasonography, and fine-needle aspiration were pursued. Thoracic radiography revealed a soft tissue nodule located within the right middle lung lobe. Ocular ultrasonography revealed a firm palpable ovoid soft tissue mass (approx 9 X 14 mm) of the medial canthus causing compression of the adjacent medial aspect of the globe. There was a mild to moderate thickening of the adjacent medial soft tissues of the orbit leading to mild flattening of the craniomedial aspect of the globe and lateral displacement. No evidence of invasion into the adjacent bone or globe was appreciated.

Formulate differential diagnoses, then continue reading.

Cytologic Findings

A fine-needle aspirate sample of the OD third eyelid mass was obtained via ultrasound guidance. The sample was submitted for cytologic interpretation by CSU’s Veterinary Diagnostic Laboratory. Following routine staining with Wright-Giemsa stain, the sample was moderately to highly cellular with a large amount of blood contamination. Cells were arranged individually and in small aggregates. They had abundant rounded to wispy to spindle-shaped basophilic cytoplasm, large ovoid nuclei with stippled chromatin, and large prominent nucleoli with some nucleoli being angular. Cells displayed moderate anisocytosis and anisokaryosis with rare binucleate cells observed. The cytologic presentation was consistent with sarcoma. Some cells contained several small cytoplasmic eosinophilic granules. The rounded cells had a plasmacytoid appearance with an eccentrically placed nucleus. Some aggregates of cells were closely associated with deeply eosinophilic fibrinous to smooth pools of extracellular matrix that was interpreted as potential osteoid. One large multinucleated cell, suspected to have been an osteoclast, was also observed.

Differential diagnoses included soft tissue sarcoma, osteosarcoma, and chondrosarcoma. To help differentiate the tumor type, the sample was tested for alkaline phosphatase activity. The results were strongly positive, indicating that the cells were likely of osteoblastic origin and suggesting a diagnosis of osteosarcoma (Figure 2). However, positive alkaline phosphatase activity has also been seen in other bone-forming tumors such as multilobular tumor of bone (MTB) or from a reactive bone lesion; thus, these etiologies cannot be ruled out at this time.2

Figure 2
Figure 2

Photomicrographs of ultrasound-guided fine-needle aspirate samples of an OD orbital mass of the dog described in Figure 1 showing eosinophilic product (arrows) within cells and extracellularly (potential osteoid), cells with abundant rounded to wispy to spindle-shaped basophilic cytoplasm, large ovoid nuclei with stippled chromatin, large prominent nucleoli, moderate anisocytosis and anisokaryosis, and rare binucleate cells. A and B—Modified Romanowsky stain; bar = 20 µm and 10 µm, respectively. C and D—Wright-Giemsa stain; bar = 20 µm and 10 µm, respectively. E and F—Wright-Giemsa stain followed by a 1-hour incubation with nitroblue tetrazolium chloride/5-bromo-4-chloro-3-indoyl phosphate toluidine salt substrate (this substrate is converted by alkaline phosphatase to stain cells that produce alkaline phosphatase black.); bar = 20 µm and 10 µm, respectively.

Citation: Journal of the American Veterinary Medical Association 259, S2; 10.2460/javma.20.03.0155

Histopathologic Findings

Due to discomfort caused by the mass, a palliative subconjunctival enucleation OD as well as a diagnostic incisional wedge biopsy of the mass was elected by the owner. The owner also elected to have the vascularized mass on the palpebral surface of the third eyelid OS excised followed by 2 cycles of cryotherapy to help prevent a recurrence. The owners did not wish to submit the third eyelid mass OS for evaluation due to financial concerns. This mass did not recur and was clinically suspected to have been a benign hemangioma.

The OD globe and biopsy sample were submitted to the Comparative Ocular Pathology Laboratory of Wisconsin for histopathologic evaluation, which revealed neoplastic cells infiltrating adipose tissue and collagen. Neoplastic cells also were observed in most of the examined tissue margins. The neoplasm was arranged in multiple distinct lobules. The center of each lobule had deposits of woven trabeculae, heavily mineralized material, and occasional cells within clear spaces determined as bone. These boney cores were surrounded by layers of neoplastic cells. These neoplastic cells were polygonal to spindle shaped with moderate amounts of amphophilic to lightly basophilic cytoplasm, typically indistinct cell borders, and round to oval nuclei with finely stippled chromatin. Anisocytosis and anisokaryosis were mild and no mitotic figures were seen per 10 hpf (Figure 3).

Figure 3
Figure 3

Photomicrographs of tissue sections from an OD orbital mass removed from the dog described in Figure 1. A—Repeating nodular pattern (asterisks) with mineralized bone (arrows) in the center of each nodule. Bland spindle cells (star) surround the mineralized bone. H&E stain; bar = 200 µm. B—Higher magnification showing the same nodular pattern (asterisk), with mineralized bone (arrows) surrounded by spindle cells (star). H&E stain; bar = 100 µm.

Citation: Journal of the American Veterinary Medical Association 259, S2; 10.2460/javma.20.03.0155

The histopathologic findings of the globe OD revealed a preiridal fibrovascular membrane covering the anterior iris surface, as well as posterior synechiae and mild entropion uveae. The preiridal fibrovascular membrane, posterior synechiae, and entropion uveae OD were supportive of the gross findings of anterior uveitis. There were few lymphocytes and plasma cells infiltrating the iris and ciliary body stroma. The lens epithelium displayed multifocal to focally extensive fibrous metaplasia, focally extensive cortical lens fiber liquefaction, and posterior migration of the lens epithelium indicating cataracts. The rest of the globe appeared normal.

Morphologic Diagnosis and Case Summary

The primary histopathologic diagnosis was right orbital or periocular MTB in an 11-year-old spayed female dog. Secondary diagnoses included lymphoplasmacytic anterior uveitis with preiridal fibrovascular membrane, posterior synechiae, mild entropion uveae, and cortical cataracts.

Comments

Palliative radiation treatment was recommended but was declined by the owner. The owner elected to monitor the dog at home for any progression. The patient was euthanized 224 days (7 months and 10 days) after palliative enucleation and biopsy surgery by the referral veterinarian due to decreased life quality according to the owner. The mass OD had increased in size and had made the right side of the skull malformed.

Enophthalmos in dogs can have various underlying etiologies. It can either be a primary (idiopathic) condition involving the orbit, or a secondary condition (infectious, inflammatory, neoplastic) that may extend from surrounding tissues such as muscles of mastication, globe, oral cavity, brain, nasal sinuses, or as in this case from orbital bone. Some shared clinical findings of these conditions include protrusion of the third eyelid, decreased or increased globe motility, signs of periocular pain, ocular discharge, conjunctival hyperemia, restricted retropulsion, and anterior uveitis.39 Enophthalmos together with prolapse of the third eyelid, as well as the dyscoric pupil OD, which could have been perceived as a miotic pupil to the referral veterinarian, may have been why Horner’s syndrome was initially suspected. Another finding for Horner’s syndrome is ptosis, which was not appreciated in this case.10

Based on the cytologic and histopathologic findings, a diagnosis of MTB was confirmed for the dog in this case report. MTB is a slow-growing nodular tumor of the membranous flat bones of the canine skull and the hard palate that usually arises from connective tissue suture lines.11 This neoplastic lesion is locally aggressive and can go through progressive malignant changes.11 Even though MTBs are considered slow-growing tumors, recurrence is expected without tumor-free histologic tissue margins, and recurrence can occur even with tumor-free histologic margins depending on the tumor grade. Malignant transformation and metastasis to the lungs can occur late during disease.12,13 A soft tissue nodule was found on thoracic radiography performed at the dog’s recheck examination at CSU-VTH. This soft tissue nodule could have been a metastasis from the MTB or it could have been a granuloma or a benign osteoma. This is only speculation because no biopsy sample was collected from the nodule, and thoracic radiography was not repeated 4 to 6 weeks following the initial radiographic examination to look for any progression.

MTBs can exhibit similar clinical appearances to other skull tumors, as well as retrobulbar and periorbital abscesses and foreign body granulomas. Thus differentiation from other tumors as well as from orbital abscesses and granulomas should be warranted.14,15 Ultrasonographic examination is the least invasive, least expensive, and widely available imaging modality to differentiate an abscess from a mass.16 However, advanced imaging such as CT and MRI can identify a solitary sharply demarcated mass arising from the skull to support a diagnosis as well. Ultimately, histopathologic evaluation is necessary for a definitive diagnosis. A study by Hendrix and Gelatt17 regarding MTBs shows that evaluation of surgical biopsy samples was diagnostic 100% of the time, whereas the combination of a fine-needle aspirate and nonsurgical biopsy (performed with a trephine or biopsy needle) evaluation was only diagnostic 79% of the time. Clinical signs that are consistent with orbital MTB in a dog include palpation of a firm fixed mass, signs of discomfort, exophthalmos, and elevation of the third eyelid, which could be secondary to the mass or pain from intraocular inflammation (uveitis).14,18,19 This supports the findings seen in our patient. The dog of the present report also had evidence of immature cataracts and an irregularly shaped pupil OD most likely secondary to posterior synechiae from secondary anterior uveitis. Our patient did not have exophthalmos, but instead, the ventromedial orbital mass caused the globe to have been deviated laterally leading to enophthalmos. We, therefore, suggest adding enophthalmos to the list of clinical signs for MTB in dogs.

A study20 involving 39 dogs with MTB had clinical findings similar to those in the dog of the present report, except for enophthalmos. A firm and fixed mass was found in 21 (54%) of the cases, whereas a mass and exophthalmos were found in 4 (10%) of the cases, and exophthalmos and signs of pain were found in only 2 (5%) of the cases (n = 2). Of those 39 dogs, 5 (13%) were not treated whereas the other 34 (87%) were treated with either surgery alone (maxillectomies, mandibulectomies, orbitectomies, partial craniectomies, and combination surgeries) or surgery coupled with adjuvant therapies (implantation with a biodegradable cisplatin polymer, administration of external beam radiation therapy, or a combination of both).20 In our case, a palliative subconjunctival enucleation was performed OD followed by a diagnostic incisional wedge biopsy of the mass for histopathologic evaluation. No further debulking of the mass was performed due to the aggressively infiltrative nature of the tumor and location. In addition, the owner declined follow-up adjuvant treatments. Time to local recurrence may differ substantially depending on the completeness of excision. A study20 shows that duration between surgery and local recurrence for dogs with incomplete margins ranged between 30 and 782 days, compared with 165 to 1,332 days for dogs with complete margins. The dog of the present report was euthanized due to disease progression 224 days after enucleation. This dog had an incisional wedge biopsy with incomplete margins, and postoperative disease progression time falls within the published range for incomplete margins of MTB in dogs.20 The biopsy sample that was submitted from this case was assessed using the published grading system for MTB and was graded as a low grade I (grading scale between 1 and 3 with 1 being the lowest).20,21

In summary, this case revealed that MTB should be considered as a differential diagnosis for a ventromedial firm soft tissue mass associated with the third eyelid in dogs with clinical signs of enophthalmos and anterior uveitis. Our findings also supported histopathologic evaluation as the most reliable way to get a definitive diagnosis of MTB.

References

  • 1.

    Maggs DJ. The ophthalmic examination and diagnostic testing. In: Maggs DJ, Miller PE, Ofri R, eds. Slatter’s Fundamental of Veterinary Ophthalmology. 6th ed. St. Louis, MO: Saunders Elsevier; 2018:1850.

    • Search Google Scholar
    • Export Citation
  • 2.

    Barger A, Graca R, Bailey K, et al. Use of alkaline phosphatase staining to differentiate canine osteosarcoma from other vimentin-positive tumors. Vet Pathol. 2005;42(2):161165.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Ramsey DT, Marretta SM, Hamor RE, et al. Ophthalmic manifestations and complications of dental disease in dogs and cats. J Am Anim Hosp Assoc. 1996;32:215224.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Holscher MA, Netsky MG, Lee TT, et al. Granular cell myoblastoma (schwannoma) in the orbit and cerebrum of two dogs. Canine Pract. 1983;10:3538.

    • Search Google Scholar
    • Export Citation
  • 5.

    Kitagawa M, Okada M, Watari T, Sato T, Kanayama K, Sakai T. Ocular granulomatous meningoencephalomyelitis in a dog: magnetic resonance images and clinical findings. J. Vet. Med. Sci. 2009;71:233237.

    • Search Google Scholar
    • Export Citation
  • 6.

    Collinson PN, Peiffer RL. Clinical presentation, morphology and behavior of primary choroidal melanomas in eight dogs. Prog Comp Vet Ophthalmol. 1993;3:158164.

    • Search Google Scholar
    • Export Citation
  • 7.

    Voges AK, Ackerman N. Magnetic resonance evaluation of intra and extracranial extension of nasal adenocarcinoma in a dog and cat. Vet Radiol Ultrasound. 1995;36:196200.

    • Search Google Scholar
    • Export Citation
  • 8.

    Burk RL. Computer tomographic imaging of nasal disease in 100 dogs. Vet Radiol Ultrasound. 1992;33:177180.

  • 9.

    Dennis R, Barnett KC, Sansom J, et al. Unilateral exophthalmos and strabismus due to cranio-mandibular osteopathy. J Small Anim Pract. 1993;34:457461.

    • Search Google Scholar
    • Export Citation
  • 10.

    Ofri R. Neuroophthalmic diseases. In: Maggs DJ, Miller PE, Ofri R, eds. Slatter’s Fundamental of Veterinary Ophthalmology. 6th ed. St. Louis, MO: Saunders Elsevier; 2018:390431.

    • Search Google Scholar
    • Export Citation
  • 11.

    Pool RR. Tumors of bone and cartilage. In: Moulton JE, ed. Tumors of Domestic Animals. 3rd ed. Berkeley, CA: University of California Press; 1990:157230.

    • Search Google Scholar
    • Export Citation
  • 12.

    Diamond SS, Raflo CP, Anderson MP. Multilobular osteosarcoma in the dog. Vet Pathol. 1980;17:759763.

  • 13.

    Losco PE, Diters RW, Walsii KM. Canine multilobular osteosarcoma of the skull with metastasis. J Comp Pathol. 1984;94:621624.

  • 14.

    McCalla TL, Moore CP, Turk J, Collier LL, Pope ER. Multilobular osteosarcoma of the mandible and orbit in a dog. Vet Pathol. 1989;26(1):9294.

    • Search Google Scholar
    • Export Citation
  • 15.

    Rühli MB, Spiess BM. Retrobulbar space-occupying lesions in dogs and cats: symptoms and diagnosis. Tierarztl Prax. 1995;23:306312.

  • 16.

    Mason DR, Lamb CR, McLellan GJ. Ultrasonographic findings in 50 dogs with retrobulbar disease. J Am Anim Hosp Assoc. 2001;37(6):557562.

  • 17.

    Hendrix DVH, Gelatt KN. Diagnosis, treatment and outcome of orbital neoplasia in dogs: a retrospective study of 44 cases. J Small Anim Pract. 2000;41:105108.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18.

    Cook CS. Diseases of the orbit. In: Morgan RV, ed. Handbook of Small Animal Practice. 3rd ed. Philadelphia, PA: Saunders; 1997:10761084.

    • Search Google Scholar
    • Export Citation
  • 19.

    Spiess M, Wallin H, Kanson N. Diseases of the canine orbit. In: Gelatt KN, ed. Verterinary Ophthalmolog. 3rd ed. Philadelphia, PA: Lipponcott, Williams, and Wilkins; 1997:511533.

    • Search Google Scholar
    • Export Citation
  • 20.

    Dernell WS, Straw RC, Cooper MF, Powers BE, LaRue SM, Withrow SJ. Multilobular osteochondrosarcoma in 39 dogs: 1979–1993. J Am Anim Hosp Assoc. 1998;34(1):1118.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21.

    Straw RC, LeCouteur RA, Powers BE, Withrow SJ. Multilobular osteochondrosarcoma of the canine skull: 16 cases (1978–1988). J Am Vet Med Assoc. 1989;195:17641769.

    • PubMed
    • Search Google Scholar
    • Export Citation

Contributor Notes

Corresponding author: Dr. de Linde Henriksen (michala.henriksen@colostate.edu)