IMAGING FEATURES OF ORBITAL MYXOSARCOMA IN DOGS

IMAGING FEATURES OF ORBITAL MYXOSARCOMA IN DOGS

RUTH DENNIS

Myxomas and myxosarcomas are infiltrative connective tissue tumors of fibroblastic origin that can be dis-

tinguished by the presence of abundant mucinous stroma. This paper describes the clinical and imaging features

of orbital myxosarcoma in five dogs and suggests a predilection for the orbit. The main clinical signs were slowly

progressive exophthalmos with soft swelling of the pterygopalatine fossa, and in two dogs, of the periorbital

area. No pain was associated with the eye or orbit but one dog had pain on opening the mouth. The dogs were

imaged using combinations of ultrasonography, radiography, and magnetic resonance imaging. In four dogs,

extensive fluid-filled cavities in the orbit and fascial planes were seen and in the fifth dog, the tumor appeared

more solid with small, peripheral cystic areas. In all dogs, the lesion extended along fascial planes to involve the

temporomandibular joint, with osteolysis demonstrable in two dogs. Fluid aspirated from the cystic areas was

viscous and sticky, mimicking that from a salivary mucocoele. Myxomas and myxosarcomas are known to be

infiltrative and not readily amenable to surgical removal but their clinical course seems to be slow, with a

reasonable survival time with palliative treatment. In humans, a juxta-articular form is recognized in which a

prominent feature is the presence of dilated, cyst-like spaces filled with mucinous material. It is postulated that

orbital myxosarcoma in dogs may be similar to the juxta-articular form in man, and may arise from the

temporomandibular joint. Veterinary Radiology & Ultrasound, Vol. 49, No. 3, 2008, pp 256–263.

Key words: dog, magnetic resonance imaging, myxosarcoma, orbit.

Introduction

MYXOSARCOMAS AND THEIR benign counterpart my-

xomas are tumors of primitive fibroblastic origin that

are characterized by an abundant, intercellular, mucinous

ground substance. Grossly, they appear as soft, pale, poorly

defined masses which exude a clear, tenacious fluid.1–4 They

are rare in dogs, but have been reported to arise from a wide

range of connective tissue sites in the body.1–4

In five dogs examined at the Animal Health Trust be-

tween 1993 and 2005 for investigation of exophthalmos,

the final diagnosis was myxosarcoma involving the orbit.

Radiography of the skull was performed in three dogs,

ultrasonography of the orbit in four dogs and magnetic

resonance (MR) imaging of the head in four dogs. Patient

information, imaging findings, and outcome are described.

Patient Information

The patients comprised two Labrador Retrievers, one

Golden Retriever, and two crossbreds weighing 19 and

30kg. They were aged between 8 and 14 years; three were

female (two neutered) and two were male (both neutered).

In all dogs, third eyelid protrusion had progressed to

exophthalmos over a period of time varying from 4 weeks

to 1 year. The left eye was affected in four dogs and the

right eye in the remaining dog. In one dog, the initial

presenting sign had been development of painless, fluctuant

soft tissue swellings ventral to the eye and in another dog,

pain on opening the mouth had been noted several days

before referral. In two dogs, the referring veterinarians

had lanced and flushed an oral swelling ventral to the

orbit, obtaining clear, viscous material in both dogs. Fluid

analysis in one of these dogs was consistent with salivary

mucocoele, but excisional biopsy of the surrounding tissue

had been unremarkable.

All five dogs showed third eyelid protrusion and marked

exophthalmos. In two dogs, the eye was also deviated dor-

sally or laterally. Retropulsion of the eye was relatively easy

and painless in all dogs, although the clinical records did

not record comparison of ease of retropulsion with the

normal eye. The affected eye was visual in four dogs and

blind in the fifth dog. Fluctuant soft tissue swelling was

present in the periocular area in two dogs and ventral to the

tongue in a third. In all dogs, swelling of the pterygopal-

atine fossa was evident on oral examination, varying from

mild to marked. One dog had pain when the mouth was

opened. The dogs were admitted for further investigations.

Ultrasonography

Four dogs underwent ocular ultrasonography and in

each one, pockets of anechoic retrobulbar fluid were found

This paper was presented at the International Veterinary RadiologyAssociation Meeting 2006, Vancouver.

Address correspondence and reprint requests to Ruth Dennis, at theabove address. E-mail: [email protected]

Received February 21, 2007; accepted for publication November 3,2007.

doi: 10.1111/j.1740-8261.2008.00361.x

From the Centre for Small Animal Studies, Animal Health Trust, Lan-wades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK.

256

(Fig. 1A and B). These varied in size from approximately

1–2.5 cm diameter and in two dogs were multiple. A hype-

rechoic margin to the fluid accumulation was reported in

two dogs and in a third dog, the fluid appeared to surround

an irregular, echogenic mass (Fig. 1C). The relatively

anechoic appearance of the fluid suggested that these were

not abscesses.

Radiography

Skull radiographs were obtained in three dogs. In the

dog with pain on opening the mouth, permeative osteolysis

of both the mandibular fossa of the temporal bone and the

mandibular condyloid process was evident (Fig. 2). This

was the dog in which fluid had appeared to surround an

echogenic mass on orbital ultrasonography. A zygomatic

sialogram was performed and was unremarkable except for

compression of the caudal aspect of the salivary gland.

Skull radiographs of a second dog had been made by

the referring veterinarian and were said to be normal but

were not submitted at the time of referral. However, upon

retrospective examination of these radiographs, there was

osteolysis of the mandible and temporomandibular joint.

Thoracic radiography was performed in all five dogs and

pulmonary metastasis was not detected.

MR Imaging

MR imaging was performed in four dogs. In all dogs,

extensive disease was present within and beyond the con-

fines of the orbit, the largest lesion measuring approxi-

mately 4 cm transversely, 13 cm dorsoventrally, and 12 cm

rostrocaudally. This resulted in varying degrees of exopht-

halmos and pterygopalatine fossa swelling. In three dogs,

the lesion consisted almost entirely of communicating, flu-

id-filled cavities with small areas of solid tissue caudally

(Fig. 3A and B). In one dog, these cystic areas were highly

complex giving a multiloculated appearance (Fig. 4A–C).

In the fourth dog, the mass was predominantly solid and

lobulated although small fluid pockets were identified

caudoventrally, near the temporomandibular joint (Fig.

Fig. 1. (A) Oblique dorsal plane ultrasonogram of the eye and orbit of a 12-year-old female entire crossbred dog. There is a discrete, anechoic structure in theorbit (white �) which was part of an extensive, multilocular/tubular cystic mass. (B) Oblique dorsal plane ultrasonogram of the eye and orbit of a 14-year-oldmale neutered crossbred dog. Note the cystic lesion abutting the back of the globe (white �). (C) Oblique dorsal plane ultrasonogram of the eye and orbit of an11-year-old female neutered Labrador Retriever. Note the well-defined area of fluid accumulation (white �) surrounding an irregular, echogenic mass (black �).

Fig. 2. Dorsoventral skull radiograph of an 11-year-old female neuteredLabrador Retriever. There is irregular osteolysis of both the mandibularfossa and the mandibular condyloid process of the temporomandibular joint;same dog as in Fig. 1C.

Fig. 3. Transverse, postcontrast, fat-suppressed, fast spin echo T1W(TR¼ 550ms and TE¼ 15ms) MR images at the level of the mid orbit (A)and the temporomandibular joint (B) in a 12-year-old female entire cross-bred dog; same dog as in Fig. 1A. There is a large orbital lesion which ismainly cystic (white �) but which is surrounded by a rim of enhancing softtissue. The lesion becomes more solid as it extends caudally towards the TMJ(arrow). Fluid within the lesion was slightly hyperintense to CSF.

257IMAGING FEATURES OF ORBITAL MYXOSARCOMA IN FIVE DOGSVol. 49, No. 3

5A–C). This dog had undergone MR imaging elsewhere 10

months previously and there was remarkably little change,

other than mild increase in size. All lesions were well de-

fined and appeared to lie mainly within fascial planes

rather than invading soft tissues, extending caudally be-

tween the zygomatic salivary gland and pterygoid muscles

medially, and the mandibular coronoid process and tem-

poral muscle laterally. All had intimate contact with the

temporomandibular joint, either contacting it medially

(two dogs) or encircling it (two dogs) (Fig. 6A and B). In

one dog, the cystic orbital mass also extended rostrally in

the intermandibular space (Fig. 4A).

In the three dogs with predominantly cystic lesions, the

fluid was isointense to CSF on T2W images and slightly

hyperintense to CSF on T1W images (Fig. 3A). Admin-

istration of intravenous contrast medium (gadobenate

dimeglumine� at 1ml/10kg) resulted in marked peripher-

al enhancement of the fluid-filled areas and also of the

small areas of more solid tissue abutting the temporoman-

dibular joints (Fig. 3A and B). The mainly solid soft tissue

mass in the fourth dog was of heterogeneous, moderately

hyperintense signal intensity on T2W images, was mildly

hyperintense to muscle on T1W images and had only

slight, patchy contrast enhancement with a wispy appear-

ance suggesting poor vascularization (Fig. 5A–C).

In the dog with the large, complex, cystic lesion, marked

osteolysis of the lateral aspect of the cranium, the coronoid

process of the mandible and the temporomandibular joint

was evident (Fig. 7A–C). In another dog, MR imaging

allowed identification of subtle signal changes of the man-

dibular condyloid process in the temporomandibular joint,

which were suggestive of minor osteolysis.

Further Tests and Outcome

In the dog with marked temporomandibular joint

osteolysis on radiographs (Figs. 1C and 2) excision arthro-

plasty of the temporomandibular joint was performed for

diagnostic and therapeutic purposes. MR imaging had not

been performed on this dog. Following decalcification of

the bone, a diagnosis of widely infiltrative myxosarcoma

was made. The owners were informed that local tumor

recurrence was likely and the dog was subsequently lost to

follow-up.

Surgical biopsy was undertaken of the dog with the

predominantly solid orbital mass (Fig. 5A–C) and the

histologic diagnosis was myxosarcoma. Based on the size

of the mass, neither surgery nor radiotherapy was consid-

ered viable options and it was recommended that the dog

be treated with analgesic medications.

The remaining three dogs had lesions with a significant

cystic component on MR images. Aspiration of the tumor

via the pterygopalatine fossa yielded tenacious, clear to

pink-tinged fluid in all dogs. The fluid was mucinous, pro-

teinaceous and of low cellularity with scattered, well-differ-

entiated epithelial cells. Biopsies were performed in two

dogs and they contained small amounts of salivary tissue.

The tentative histopathologic diagnosis was sialocoele in

two dogs and mucus-producing salivary adenoma in the

third although the presence of osteolysis on MR imaging in

one of these dogs suggested a more aggressive process. All

of these three dogs underwent subsequent palliative sur-

gery. Marsupialization of the intermandibular portion of

the lesion was performed in one dog (Figs. 4A–C, 6B and

7A–C) and a large volume of thick, mucinous fluid was

released. Within a few days, the exophthalmos resolved

and vision returned to the previously blind eye. Six months

later, the dog had recurrent severe, recurrent exophthal-

mos. Repeat MR images were basically unchanged.

An excisional biopsy obtained post-mortem confirmed a

myxosarcoma.

Surgical biopsy and lesion drainage was also performed

on another dog (Figs. 1A, 3A, B and 6A) and myxosar-

coma was diagnosed histopathologically. The exophthal-

mos was slightly reduced by the surgery but subsequently

recurred. The dog was managed for a further 10 months

Fig. 4. Transverse (A), dorsal (B), and sagittal (C) fast spin echo T2W (TR¼ 6000ms and TE¼ 84ms) MR images of a 9-year-old female neutered LabradorRetriever. Note the extensive, multiloculated fluid accumulation in the orbit, extending rostrally in the intermandibular space and caudally to the tempo-romandibular joint.

�Multihances

, Bracco, Milan, Italy.

258 DENNIS 2008

with symptomatic therapy and repeated fluid drainage via

the pterygopalatine fossa.

A similar procedure was carried out on another dog

(Fig. 1B) and myxosarcoma was confirmed from a biopsy.

The procedure resulted in reduction of the exophthalmos

but it did not completely resolve. In an MR imaging study

repeated 5 months later, the lesion was essentially un-

changed. The dog was still alive and clinically unchanged

9 months after the original investigation.

Discussion

Myxosarcomas are malignant tumors of primitive

pleomorphic mesenchymal cells in which altered fibro-

blasts produce excessive mucin. They consist of loosely

arranged stellate or spindle-shaped cells separated by an

abundant mucinous matrix rich in mucopolysaccharides,

which stain characteristically with Alcian blue.1–4 The term

myxoid or myxomatous indicates a loose mesenchymal

arrangement with a stroma containing mucinous material,

and the presence of this stroma is the chief feature that

distinguishes myxosarcoma and its benign counterpart my-

xoma from fibrosarcomas and fibromas, although the dis-

tinction may not always be clear.3,5 Histologic diagnosis

is also difficult due to the paucity of cells that may be pres-

ent in a sample and the fact that significant myxomatous

change may also be seen in a number of other tumor types,

including chondrosarcoma, liposarcoma, hemangiopericy-

toma, schwannoma, synovial sarcoma, smooth muscle tu-

mors, embryonal rhabdomyosarcoma, neurofibroma, and

mucinous adenocarcinoma. Myxoid changes may also be

seen in benign conditions of the skin and subcutis such as

localized myxoedema or mucous cysts.1,2,5

The gross appearance of a myxosarcoma or myxoma is

of a soft, pale, poorly defined mass which exudes a clear,

viscid, honey-like fluid from its cut surfaces.2,3,6 Cytologic

smears are often difficult to prepare because of the slimy

consistency of the specimen and the relative lack of cells

adhering to the slide. Histopathologic differentiation be-

tween myxosarcoma and myxoma may be difficult since

differences between the two may be subtle.1–3,7 The malig-

nant form tends to be more cellular, better vascularized

and has nuclear pleomorphism and mitotic figures. Dis-

tinction between the benign and malignant form of the

disease may be somewhat academic, since both myxoma

and myxosarcoma are ill-defined, infiltrative growths in

which recurrence after removal is highly possible.1,2,4,8

However, growth may be slow in some patients as borne

out by several of the dogs in this report.9 Metastasis may

occur with myxosarcoma but is rare,1,2,4 and was not

detected in any of these five dogs.

Myxosarcomas in humans are rare, and arise primarily

in the heart.10,11 Only three orbital myxosarcomas are

reported.12–14 Benign myxomas are also uncommon

and most often arise in the heart and in skeletal muscle.

They may also occur in other soft tissues and in bone15 but

only 11 myxomas involving the orbit in humans are

recorded.8,16–20 Two types of myxoma are recognized:

Fig. 5. Transverse fast spin echo precontrast T1W (TR¼ 600ms and TE¼ 12ms) (A), postcontrast T1W (B) and T2W (TR¼ 4000ms and TE¼ 88ms) (C)MR images of an 8-year-old male neutered Golden Retriever at the level of the caudal orbit. A large, heterogeneous mass is seen medial, dorsal and lateral tothe coronoid process of the mandible and within a fascial plane near the orbital apex (arrow). The mass is subtly hyperintense to muscle on precontrast T1W,and has slight, uneven contrast enhancement indicating that it is poorly vascularized. On the T2W image, it is of mixed signal intensity and although mainlyappearing solid, small fluid pockets are present caudoventrally (arrowheads).

Fig. 6. (A) Transverse fast spin echo T2W (TR¼ 4320ms andTE¼ 83ms) MR image of a 12-year-old female entire crossbred dog at thelevel of the temporomandibular joint; same dog as in Figs. 1A, 3A and 3B. Ahyperintense soft tissue mass lies medial to the temporomandibular joint(arrow) but there is no obvious osteolysis. (B) Transverse fast spin echo T2W(TR¼ 6000ms and TE¼ 84ms) MR image of a 9-year-old female neuteredLabrador Retriever. There is an irregular, hyperintense mass encircling thetemporomandibular joint; same dog as in Fig. 4A–C.


intramuscular (usually in the thigh) and, less commonly,

juxta-articular (usually around the knee). In the intramus-

cular form, little or no cystic change is present whereas a

characteristic feature of the juxta-articular form is the

presence of dilated, cyst-like spaces filled with mucinous

ground substance.21,22 In 65 humans with juxta-articular

myxoma, 57 (88%) occurred around the knee, with a

duration of symptoms ranging from 1 week to 18 years.23

Five tumors were incidental findings during hip or knee

replacement surgery. In 29 patients, who were followed up

after surgery, the lesion recurred at least once in 10 (34%).

Although some of these lesions were found to abut syno-

vial tissue and other periarticular soft tissues or to invade

the joint itself, bone involvement was not described in any

patient. These authors considered juxta-articular myxoma

to be unquestionably benign and speculated that it might

be a reactive process secondary to constant joint motion,

rather than being neoplastic. A juxta-articular form of

myxosarcoma has not been described in humans.

None of the human orbital myxosarcoma patients had

cross-sectional imaging as they all predate the use of

computed tomography (CT) and MR imaging, but one of

the myxomas had cystic areas on ultrasonography.16 Also,

the clinical description of a myxosarcoma of the orbit in

a 6-year-old boy as a tense abscess suggested the presence

of fluid pockets.14 The other tumors appear to have been

solid, although most were described as being slippery,

sticky, soft or friable. None of the human patients had any

suggestion of involvement of the temporomandibular joint

based either on clinical signs or imaging findings. Causes

of orbital lesions with cystic components in man include

dermoid cyst and other congenital anomalies which may

present later in life: parasitic cyst, chronic hematic cysts

(cholesterol granulomas), lymphangioma, lacrimal duct

cyst, and mucocoele.24

Myxosarcomas and myxomas are rare in other animals

except for chickens and rabbits in which they have a viral

etiology.1,3 They have been reported in the horse, ox,

sheep, dog, and cat3 and in several exotic species.25,26 Older

animals are affected, with no breed or sex prevalence.3 In

this series, the dogs were aged between 8 and 12 years old;

two were male and three female. All were medium or large

dogs. Myxomas are reported more frequently in dogs and

myxosarcomas appear to be rare.27 Both tumors arise in

connective tissue, and sites in which both myxomas and

myxosarcomas have been seen in the dog include the skin

and subcutis, heart, liver, mouth, limbs and spine, and as

components of mixed mammary tumors.2–5,27–33 Myxosar-

comas have also been reported in the intestine, spleen,

mesentery, and urethra in dogs2,6,9,34–38 and two previous

dogs with myxosarcoma involving the orbit have been de-

scribed.39,40 During the time scale over which the five dogs

reported here were seen, only one other myxosarcoma was

diagnosed in our clinic, being on the paw of an 8-year-old

Lakeland Terrier. This suggests that the orbit may be a

predilection site for myxosarcoma in the dog.

A morphologically distinct entity of synovial myxoma

was considered to be present in three dogs in which syno-

vial tissue was involved in a myxoma.41 Two of these

tumors arose at the stifle and one at the articular process

joint of C2–3. A synovial myxoma involving the stifle of

a dog has been reported32 and a synovial myxosarcoma has

also been reported in this location.4 In both of these dogs,

there was evidence of bone invasion. In another dog,

a myxoma of the carpus was described as being attached

to the antebrachiocarpal joint capsule by a stalk and to

contain gelatinous, mucoid material on transection, and it

is probable that this also represented a synovial variant.42

Possibly such synovial myxomas and myxosarcomas are

equivalent to the juxta-articular form described in humans,

similarities being their proximity to joints and the abun-

dance of mucinous ground substance present. In the five

dogs with orbital myxosarcoma described here, involve-

ment of the temporomandibular joint was present or

suspected in all five and pockets of fluid were also present

in all five cases, being very extensive in four. These orbital

Fig. 7. Dorsal (A and B) and transverse (C) T2� gradient echo (TR¼ 600ms, TE¼ 15ms and flip angle¼ 201) MR images of a 9-year-old female neuteredLabrador Retriever. Note the osteolysis of the cranium (A—arrow), mandibular coronoid process (B—arrow) and temporomandibular joint (C—arrow) by anextensive soft tissue mass; same dog as in Figs. 4A–C and 6B.

260 DENNIS 2008

myxosarcomas, therefore, also resemble the human juxta-

articular form and may be equivalent to the synovial form

described previously in dogs.41 The large size of the tumors

in these dogs meant that biopsy was performed away from

the temporomandibular joint in four and therefore lack of

synovial tissue in the sample is not surprising. However,

juxta-articular myxomas in humans are not reported

to cause osteolysis whereas this has been seen in both

myxomas and myxosarcomas arising near joints in dogs

and suggests a more aggressive process. Detection of

temporomandibular joint osteolysis may have implications

for prognosis, because in this study, the dog with the most

marked osteolysis also had severe pain on mouth-opening.

In the five dogs described here, exophthalmos had been

present for periods varying between several weeks and

1 year before presentation. Two dogs also had soft,

fluctuant swelling around the eye in which one was appar-

ently acute in onset, and all five had varying degrees of

swelling of the pterygopalatine fossa ventral to the orbit.

Interestingly, although comparison with the opposite eye

was not recorded, reduction in retropulsion was not a

significant feature in these five dogs, presumably reflecting

the fact that these orbital masses are soft and may contain

large amounts of fluid. In none of the dogs was pain on

retropulsion a feature of the disease, although one dog had

marked discomfort on eating. Another dog also had severe

bony involvement of the temporomandibular joint, but

there were no associated clinical signs. One dog was blind

in the affected eye.

Radiographic changes in the orbit suggest a poor prog-

nosis as orbital disease must be extensive for this change to

occur. In dogs where the tumor remains confined to the

orbit, radiographs will be normal except for soft tissue

swelling caused by displacement of the eyeball. However,

false-negative radiographic results occur when extension of

the tumor is present but is not severe enough to be radio-

graphically evident.43 In this series, two dogs had osteolytic

radiographic changes affecting the temporomandibular

joint; thus, orbital myxosarcomas may involve this joint.

In this series, anechoic fluid pockets were readily

identified in the four dogs that underwent ultrasonography

and relative lack of internal echoes together with absence

of pain suggested that abscessation was unlikely. In one

dog, multiple, large, cystic areas with thick, echogenic

borders were seen, and ultrasound guidance was used for

aspiration of the contents. Although ultrasonography

allowed identification of the cystic orbital lesion, it failed

to allow determination of the extent of the mass in all dogs.

Ultrasonographic results may, therefore, suggest an orbital

myxosarcoma, especially if aspiration of the lesion yields

tenacious fluid, but further imaging is required to assess its

full extent.

MR imaging was performed in four of the five dogs

described here and the extent of the solid and cystic com-

ponents of the tumors, as well as larger areas of osteolysis,

were readily apparent. The most helpful MR sequence was

T2W because of the high contrast between fluid and soft

tissue, which showed the loculated nature of the tumor.

The fluid seen in the cystic areas was slightly hyperintense

to CSF on T1W in all dogs, suggesting an increased protein

content. In postcontrast T1W images, the extent of the

solid component of the tumor could be evaluated, while

a STIR sequence was used in the dog with the predom-

inantly solid orbital mass and T2� gradient echo sequences

were performed in three dogs to delineate the temporo-

mandibular joint more clearly. Both cortical and medullary

bone are hypointense on T2� gradient echo sequences

which contrasts well with the hyperintense signal from ad-

jacent soft tissues and permits assessment of osteolysis. All

three orthogonal imaging planes were used and this was

helpful in understanding the three-dimensional extent of

the tumor. Although MR imaging was useful in detecting

abnormal tissue adjacent to the temporomandibular joint

in two dogs, definite osteolysis was not detected even using

multiple imaging planes and sequences, and may have been

overlooked.

CT has been used to assess orbital myxosarcoma in

dogs,44,45 though contrast resolution of CT is inferior to

that of MR imaging and CT is likely not to be as useful for

tumor staging. In the five dogs described here, it is assumed

that the large, fluid-filled pockets and areas of contrast-

enhancing soft tissue would have been visible on CT

images, but it is anticipated that the tumor margins would

not have been as discernable.

Zygomatic sialocoele is the main differential diagnosis

for an anechoic, cystic orbital mass in a dog, and was the

initial diagnosis made in one dog based on ultrasono-

graphy and radiography alone. Zygomatic sialocoeles are

uncommon and are usually the result of trauma.46,47 They

give rise to exophthalmos, painless orbital swelling and

protrusion of the oral mucosa behind the last molar tooth.

Fluid in the sialocoele is usually a tenacious, straw-colored

fluid not dissimilar to that found in myxosarcoma. A

zygomatic sialogrammay help to define the lesion and both

CT and MR imaging are useful for discrimination.47 Other

fluid-filled orbital masses in the dog include abscesses

and hematomata, but it should be possible to differentiate

these from sialocoeles and myxosarcomata on the basis of

history, clinical signs, combined imaging findings, and fine

needle aspiration.

In conclusion, myxosarcoma is a rare tumor in dogs but

may have a predilection for the orbit. In view of the pres-

ence of fluid-filled pockets, which may be extensive, and the

apparent involvement of the temporomandibular joints, the

tumors described in this report are similar to the juxta-

articular form of myxoma in man, albeit in a malignant

form. It is possible that they arose from the temporoman-

dibular joint and extended along fascial planes into the or-


bit, following a low-resistance pathway. Imaging features in

these five dogs were of orbital masses with cystic compo-

nents which were very extensive in four dogs and which

were easily seen on ultrasonography. Temporomandibular

joint osteolysis was visible radiographically in two dogs.

MR imaging allowed evaluation of the full extent of the

lesion and indicated that surgical drainage might be of

benefit. Based on these five dogs, the clinical course of the

disease may be rather indolent and relatively pain-free un-

less significant temporomandibular joint osteolysis is pres-

ent. The main differential diagnosis is zygomatic sialocoele.

Histologic diagnosis of myxosarcoma is not straightforward

and may require surgical biopsy and special staining tech-

niques. These are to be recommended in patients in which

orbital fluid pockets extending to the temporomandibular

joint are recognized on diagnostic imaging.

ACKNOWLEDGMENTS

I wish to acknowledge ophthalmology and pathology colleagues atthe Animal Health Trust who were involved with these cases, especiallyDavid Donaldson and Claudia Hartley (ophthalmology), and TonyBlunden and Ken Smith (pathology).

REFERENCES

1. Hendrick MJ, Mahaffey EA, Moore FM, Vos JH, Walder EJ.Histological classification of mesenchymal tumors of skin and soft tissues ofdomestic animals, 2nd series, Vol. 2. Washington, DC: Armed Forces In-stitute of Pathology, 1998;17–18.

2. Goldschmidt MH, Hendrick MJ. Tumors of the skin and soft tis-sues. In: Meuten DJ (ed): Tumors in domestic animals, 4th ed. Ames, IA:Iowa State Press, 2002;91–99.

3. Pulley LT, Stannard AA. Tumors of the skin and soft tissues. In:Moulton JE (ed): Tumors in domestic animals, 3rd ed. Berkeley, LA: Uni-versity of California Press, 1990;33–34.

4. Grindem CB, Riley J, Sellon R, Davis B. Myxosarcoma in a dog.Vet Clin Pathol 1990;19:119–121.

5. Williamson MM, Middleton DJ. Cutaneous soft tissue tumours indogs: classification, differentiation, and histogenesis. Vet Dermatol1998;9:43–48.

6. Weinstein MJ, Carpenter JL, Schunk CJM. Nonangiogenic andnonlymphomatous sarcomas of the canine spleen: 57 cases (1975–1987). JAm Vet Med Assoc 1989;195:784–788.

7. Thielen GH, Madewell BR. Tumors of the skin and subcutaneoustissues. In: Thielen GH, Madewell BR (eds): Veterinary cancer medicine, 2nded. Philadelphia: Lea and Febiger, 1987;290.

8. Maiuri F, Corriero G, Galicchio B, Angrisani P, Bonavolonta G.Myxoma of the skull and orbit. Neurochirurgia 1988;31:136–138.

9. Eason P. Unusual neoplasm in a dog (letter). Vet Rec 1993;133:224.10. Maitra RN, McHaffie DJ, Wakefield JS, Delahunt B. Myxosarcoma

of the right ventricle: an immunohistochemical and ultrastructural study.Anticancer Res 2003;23:3549–3553.

11. Samal AK, Ventura HO, Berman A, Okereke C, Gilliland YE, WillisGW. Myxosarcoma: a rare primary cardiac tumor. J La State Med Soc2002;154:308–312.

12. Gupta JS, Gopal H, Dhavan SK. Myxoma of the orbit (a casereport). Indian J Ophthalmol 1971;19:27–30.

13. Buckley JH. Recurring myxosarcoma of the orbit. Am J Ophthalmol1922;5:207–208.

14. Weekes JE. Report of two cases of metastatic carcinoma of thechoroid and one case of myxosarcoma of the orbit. Trans Am Ophthal Soc1915;14:326–331.

15. Anon. (editorial) Myxoma of soft tissues. Br Med J 1974;1:170.16. Rambhatla S, Subramanian N, Gandaghara Sundar JK, Krishna-

kumar S, Biswas J. Myxoma of the orbit. Indian J Ophthalmol 2003;51:85–87.

17. Craig NM, Putterman AM, Roenigk RK, Wang TD, Roenigk HH.Multiple periorbital cutaneous myxomas progressing to scleromyxedema. JAm Acad Dermatol 1996;34:928–930.

18. Candy EJ, Miller NR, Carson BS. Myxoma of bone involving theorbit. Arch Ophthalmol 1991;109:919–920.

19. Lieb WE, Goebel HH, Wallenfang T. Myxoma of the orbit: a clin-icopathologic report. Graefes Arch Clin Exp Ophthalmol 1990;228:28–32.

20. Maria DL, Marwa V. Myxoma of the orbit. J All-India OphthalmolSoc 1967;15:75–76.

21. Daliuski S, Seeger LL, Doberneck SA, Finerman GAM, Eckardt JJ.A case of juxta articular myxoma of the knee. Skeletal Radiol 1995;24:389–391.

22. King DG, Saifuddin A, Preston HV, Hardy GJ, Reeves BF. Mag-netic resonance imaging of juxta-articular myxoma. Skeletal Radiol1995;24:145–147.

23. Meis JM, Enzinger FM. Juxta-articualr myxoma: a clinical andpathologic study of 65 cases. Human Pathol 1992;23:639–646.

24. Vashisht S, Ghai S, Hatimota P, Ghai S, Betharia SM. Cystic lesionsof the orbit—a CT spectrum. Indian J Radiol Imaging 2003;13:139–144.

25. Shilton CM, Thompson MS, Meisner R, Lock B, Lindsay WA.Nasopharyngeal myxosarcoma in a Bengal tiger (Panthera tigris). J ZooWildl Med 2002;33:371–377.

26. van Zeeland YRA, Hernandez-Divers SJ, Blasier MW, Vila-GarciaG, Delong D, Stedman NL. Carapl myxosarcoma and forelimb amputationin a ferret (Mustela putorius furo). Vet Rec 2006;159:782–785.

27. Briggs OM, Kirberger RM, Goldberg NB. Right atrial myxosarco-ma in a dog. J S Afr Vet Assoc 1997;68:144–146.

28. White RAS. Mandibulectomy and maxillectomy in the dog: longterm survival in 100 cases. J Small Anim Pract 1991;32:69–74.

29. Stebbins KE, Morse CC, Goldschmidt MH. Feline oral neoplasia: a10 year study. Vet Pathol 1989;26:121–128.

30. Foale RD, White RAS, Harley R, Herrtage ME. Left ventricularmyxosarcoma in a dog. J Small Anim Pract 2003;44:503–507.

31. Levy MS, Kapatkin AS, Patnaik AK, Mauldin GN, Mauldin GE.Spinal tumors in 37 dogs: clinical outcome and long-term survival (1987–1994). J Am Anim Hosp Assoc 1997;33:307–312.

32. Hayes AM, Dennis R, Smith KC, Brearley MJ. Synovial myxoma:magnetic resonance imaging in the assessment of an unusual canine softtissue tumour. J Small Anim Pract 1999;40:489–494.

33. Atalay-Vural S, Aydn Y. A survey of canine mammary tumoursfrom 1973 to 1998 in Ankara. Turk Veterinerlik ve Hayvanclk Dergisi2001;25:233–239.

34. Reddy MV, Ramakrishna K, Mahender M. Myxosarcoma in anAlsatian dog. Malays Vet J 1978;6:207–208.

35. Hong-Sung H, Kweon-Oh K. Primary splenic myxosarcoma in adog. Korean J Vet Clin Med 2000;17:252–255.

36. Spangler WL, Culbertson MR, Kass PH. Primary mesenchymal(nonangiomatous/nonlymphomatous) neoplasms occurring in the caninespleen: anatomic classification, immunohistochemistry, and mitotic activitycorrelated with patient survival. Vet Pathol 1994;31:37–47.

37. Oliveira ST, Cunha CG, Iwanaga SH, Coelho HE, Manzan RM.Mesenteric myxosarcoma in a dog. Arq Bras Med Vet Zootec 1999;51:537–538.

38. Wilson GP, Hayes HM, Casey HW. Canine urethral cancer. J AmAnim Hosp Assoc 1979;15:741–744.

39. Gomez N, Alvarez A, Martinez MAS. Mixosarcoma orbitario. VetArgent 2001;18:310–318.

40. Richter M, Stankeova , Hauser B, Scharf G, Spiess BM. Myxosar-coma in the eye and brain in a dog. Vet Ophthalmol 2003;6:183–189.

262 DENNIS 2008

41. Pool RJ. Tumors and tumor-like lesions of the joints and soft tissues.In: Moulton JE (ed): Tumors in domestic animals, 3rd ed. Berkely, LA:University of California Press, 1990;118–119.

42. Griffon DG, Wallace LJ, Barnes DM, Johnston GR. Myxoma aris-ing from the radiocarpal joint capsule in a dog. J Am Anim Hosp Assoc1994;30:257–260.

43. Dennis R. Use of magnetic resonance imaging for the investi-gation of orbital disease in small animals. J Small Anim Pract 2000;41:145–155.

44. LeCouteur R, Fike JR, Scagliotti RH, Cann CE. Computed tomog-raphy of orbital tumours in the dog. J Am Vet Med Assoc 1982;180:910–913.

45. Calia CM, Kirschner SE, Baer KE, Stefanacci JD. The use of com-puted tomography scan for the evaluation of orbital disease in cats and dogs.Vet Comp Ophthalmol 1994;4:24–30.

46. Martin CL, Kaswan RL, Doran CC. Cystic lesions of the periorbitalregion. Compend Contin Educ Pract Vet 1987;9:1022–1029.

47. Slatter D, Basher T. The orbit. In: Slatter D (ed): Textbook of smallanimal surgery, 3rd ed. Philadelphia: Saunders, 2003;1442.


IMAGING FEATURES OF ORBITAL MYXOSARCOMA IN DOGS

Documents

Transcript of IMAGING FEATURES OF ORBITAL MYXOSARCOMA IN DOGS