Article Text

Liposarcoma of the orbit presenting as an enlarged medial rectus muscle on CT scan
  1. M L R Monteiro
  1. Division of Ophthalmology, Hospital das Clínicas of the University of São Paulo Medical School, São Paulo, Brazil
  1. Correspondence to: mlrmonteiro{at}terra.com.br

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Primary orbital liposarcoma is extremely rare in the orbit. Only a few published cases have included imaging studies, showing findings varying from well defined, homogeneous lesions of soft tissue density to heterogeneous masses containing fat.1,2 We report one patient who presented with painless proptosis and double vision and had an enlargement of the medial rectus muscle on computed tomography (CT) as the sole initial imaging finding.

Case report

A 75 year old man presented with a 3 month history of painless diplopia and protrusion of the left eye. His medical history revealed only diabetes mellitus. On ophthalmic examination his visual acuity was 6/6 in the right eye and 6/9 in the left eye. There was a reddish tumoral growth in the medial canthus of the left eye, right above the insertion of the medial rectus muscle below the conjunctiva. The left eye as dislocated laterally and anteriorly, with 2 mm of proptosis, limitation of adduction, elevation, and depression.

A CT scan was obtained and revealed marked enlargement of the medial rectus muscle throughout its extension, with enhancement after intravenous contrast administration (Fig 1). Extensive laboratory investigation including thyroid hormones and TSH was normal except for diabetes. A trial of oral prednisone (80 mg/day) was introduced for 1 week without any improvement in his condition and therefore a transconjunctival biopsy of the lesion was performed. It revealed a pleomorphic liposarcoma and a radical tumour removal was indicated. The patient was reluctant to accept it and returned only 2 months later when there was marked enlargement of the tumour. A repeat CT scan revealed that the tumour extended to the orbital fat and was now a heterogeneous lesion with central hypodense areas circumscribed by hyperdense, contrast enhancing areas (Fig 2).

Figure 1

Marked enlargement of the left medial rectus muscle on CT scan.

Figure 2

CT scan showing heterogeneous lesion with central hypodense areas circumscribed by hyperdense, contrast enhancing areas.

The patient underwent orbital exenteration followed by skin graft of the orbital cavity and postoperative orbital irradiation. There was complete removal of the tumour that was restricted to the orbit. The patient remained free of tumour for the following 6 years, when he died as a result of systemic complications after a femur fracture.

Comment

Despite the large amount of adipose tissue in the orbit, primary orbital liposarcomas are extremely rare, with only 27 cases previously reported.1–7 Metastatic orbital liposarcomas are also extremely rare with only a few cases documented in the literature.8 When liposarcoma occur in the orbit there is no specific pattern of involvement and the tumour presents marked diversity of clinical presentations. Our patient presented initially with a tumour restricted to the medial rectus muscle with a radiological appearance very similar to the metastatic liposarcoma reported by Fezza and Sinard.8 Contrary to their case, however, our patient did not have any history of systemic disease and did not develop tumour elsewhere in the body in a 6 year follow up period. Although preferential involvement of one extraocular muscle has been documented,1 to our knowledge none of the previously described cases of primary orbital liposarcoma was restricted to the extraocular muscle as in our case.

Although the differential diagnosis of extraocular muscle enlargement is extensive and includes Graves’s orbitopathy, myositis, carotid cavernous fistula, lymphoma, metastatic tumours, etc, our case shows that physicians should include a liposarcoma in differential diagnosis of patients in which the clinical and laboratory findings are not in accordance with other more common causes of extraocular muscle enlargement.

References

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