aCase 10

by Dr.Chua

A 7-year-old boy who had learning difficulty was referred  to our department from another eye unit because of a one-week history of progressive left proptosis. He was initially managed as orbital cellulitis because of a recent history of dental cary. CT scan showed a lateral orbital mass with extension into the temporal fossa and the cranium. The maxillary sinus was opaque.

Examination revealed an otherwise well child with left severe proptosis and swellings of the ipsilateral cheek and temporal fossa. There was no afferent pupillary defect. Palpation showed the proptosis was not reducible and the swellings of the cheek and temporal region were firm.
 

Figure 1. One-week history of progressive left proptosis with cheek

and temporal fossa swellings.

Figure 2. CT scans of the maxillary sinus and orbit showing opacity in the left

maxillary sinus (above) and lateral orbit, cranium and the temporal fossa.

a. Why is orbital cellulitis with subperiosteal abscess an unlikely diagnosis in this patient?

Clinically this patient is well without pyrexia which is in marked contrast to a patient with a subperiosteal abscess. In the later, the patient is usually unwell with pyrexia. There is marked preseptal cellulitis with lid swelling and chemosis.

On a CT scan, subperiosteal abscess appears as an extraconal low density fluid collection causing periosteal elevation. With contrast, the periosteal shows enhancement giving a ring-like enhancement pattern. Such ring-like enhancement or an air-fluid level within the mass
are regarded pathognomonic for a subperiosteal abscess.^1-3 These signs were absent in this patient. In addition, the lesion spread around the bone making a neoplastic process the most likely diagnosis.

b. What is the most likely diagnosis?

In a well child with a rapid onset and progression of unilateral proptosis and globe displacement over days to weeks, rhabdomyosarcoma should be the initial diagnosis until proven otherwise. Swelling and injection of the overlying skin may be present but in contrast to orbital cellulitis there is no warmth on palpation and the patient is apyrexial.⁴

Rhabdomyosarcoma is the most common primary orbital malignancy of childhood and the presentation in our patient is typical of this condition. The commonest locations are in the superonasal quadrant. The majority of the tumours are located in the extraconal compartment. The extraocular muscles are usually displaced or encased by the mass.

Histologically, it is made up of cells with the histological features of striated muscle in various stages of muscle embryogenesis. Three histological types are identified: embryonal, alveolar and pleomorphic; the embryonal and alveolar types presenting more commonly in children and the pleomorphic type presenting more commonly in adults (see case 8).

On the CT scan rhabdomyosarcomas appear as homogenous, irregularly shaped, well-defined soft-tissue masses that are isodense in relation to normal muscles. The tumours show moderate to marked contrast enhancement. Larger tumours are less well defined with bone destruction or invasion of the paranasal sinuses, nasal cavity, soft tissues or intracranial structures.^5-6

c. How would you manage this patient ?

Biopsy should be carried out to confirm the diagnosis. In our patient, biopsy from the lateral orbital mass and the temporal fossa revealed poorly differentiated round cell tumour which are consistent with an embryonal rhabdomyosarcoma. Immunostaining confirmed the tumour to be that of rhabdomyosarcoma.

Figure 3. At lateral canthotomy and cantholysis, a mass was found

attaching to the lateral rectus muscle (arrowed).

The patient was referred to the paediatric oncologist who performed further work-up to stage the tumour. Distant metastasis was present at the abdomen and this put the patient at Group IV (see grouping in the table below).⁴ The patient underwent chemotherapy but the prognosis was unfavorable.

 
Reference:

1. H.S. Eustis, M.F. Mafee, C. Walton, J. Mondonca, MR imaging and CT of orbital infections and complications in acute rhinosinusitis, Radiol. Clin. N. Am. 36 (1998)
1165–1183.

2. Moloney JR, Badham NJ, McRae A. The Acute Orbit. Preseptal (Periorbital) cellulitis, subperiosteal abscess and orbital cellulitis due to sinusitis, J Laryngol Otol 1987;101(Suppl. 12):1–18.

3. H.S. Eustis, D.C. Armstrong, J.R. Buncic, J.D. Morin. Staging of orbital cellulitis in children: Computerized tomography characteristics and treatment guidelines. J. Pediatr. Ophthalmol. Strabismus 23 (1986) 246–251.

4. Shields JA, Shields CL. Rhabdomyosarcoma: review for the ophthalmologist. Surv Ophthalmol. 2003 Jan-Feb;48(1):39-57. Review.

5. M.F. Mafee, E. Pai, B. Philip, Rhabdomyosarcoma of the orbit. Evaluation with MR Imaging and CT, Radiol. Clin. N. Am. 36 (1998) 1215–1227.

6. S.A. Sohaib, I. Moseley, J.E. Wright. Orbital rhabdomyosarcoma — the radiological characteristics. Clin. Radiol. 53 (1998) 357–362.