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Arch Ophthalmol. 2001;119:1208-1210.

Rhabdomyosarcoma is the most common primary orbital malignant neoplasm of childhood. However, it constitutes only 4% of all orbital lesions studied by biopsy in children.¹ As it is a highly malignant tumor, prompt diagnosis and treatment are imperative. Current therapeutic regimens of radiation and chemotherapy have provided 93% 3-year survival.² We herein report a rare variant of orbital rhabdomyosarcoma that showed magnetic resonance (MR) imaging findings of central cavitation, simulating an orbital lymphangioma.

Report of a Case
An otherwise healthy 4-year-old girl was referred to us because of abrupt-onset proptosis of her right eye (Figure 1). The parents had noted mild painless swelling of the right upper eyelid during the previous 3 weeks.

View larger version (6K): [in this window] [in a new window] Figure 1. Ptosis, proptosis, and inferotemporal displacement of the right eye in a 4-year-old girl.

The visual acuity was 20/20 in each eye. There was 6 mm of right proptosis. Motility was restricted in all gazes, and the right eye was displaced inferiorly and temporally. Subtle subcutaneous ecchymosis was present at the inferotemporal orbital rim. There was a dilated clear lymphatic channel on the conjunctiva superonasally.

An MR image showed a superonasal heterogeneous soft tissue mass with no bone erosion. On T1-weighted gadolinium-enhanced images, the central area of the mass was hypointense, suggestive of proteinaceous material. A peripheral hyperintense rim indicated vascularized tissue. There was a thin septum dividing the central "cystic" area, but fluid-fluid levels were not seen (Figure 2A). T2-weighted images disclosed an irregular isointense rim and central area of extreme hyperintense signal (Figure 2B). These findings were suggestive of lymphangioma with proteinaceous fluid and hemorrhage.

View larger version (22K): [in this window] [in a new window] Figure 2. A, Coronal magnetic resonance image (T1-weighted with fat suppression and gadolinium enhancement) showing a nonenhancing low-signal central area compatible with proteinaceous fluid or blood. The rim shows moderate enhancement. Note the septation within the central area. B, Coronal magnetic resonance image (T2-weighted) showing the central cavity with bright signal, again suggestive of proteinaceous fluid or blood.

A diagnosis of lymphangioma was favored in light of the rapid development of proptosis, dilated conjunctival lymphatics, subcutaneous ecchymosis, and the presence of presumed cystic, rather than solid, structures on MR imaging. Cautious observation was advised, but 10 days later, worsening of the proptosis and eyelid swelling prompted a biopsy. Intraoperatively, a multicystic blue mass was found and aspiration of 1 mL of internal serosanguineous fluid collapsed the mass. Near-total excision of the remaining mass was performed. These findings continued to suggest the diagnosis of hemorrhagic lymphangioma.

Histopathologic examination disclosed undifferentiated small round cells with hyperchromatic nuclei (Figure 3), high nuclear-to-cytoplasmic ratio, and brisk mitotic activity. Immunohistochemistry demonstrated intense immunoreactivity for smooth muscle actin and desmin. These findings confirmed the diagnosis of rhabdomyosarcoma.

View larger version (9K): [in this window] [in a new window] Figure 3. Photomicrograph showing poorly differentiated, malignant "small blue cell tumor" with occasional strap cells consistent with embryonal rhabdomyosarcoma (hematoxylin-eosin, original magnification x250).

Radiotherapy (4500 rad [45 Gy]) and chemotherapy with cyclophosphamide, dactinomycin, and vincristine sulfate were instituted by means of the Intergroup Rhabdomyosarcoma Study Committee protocol.² The patient continued to demonstrate complete tumor regression at 20 months' follow-up.

Comment
Orbital rhabdomyosarcoma typically occurs as a unilateral solid mass in the superonasal part of the orbit. The average age at diagnosis is 8 years. Proptosis and displacement of the globe usually develop during a period of weeks.³ Lymphangioma also occurs in a similar age group, about 4 to 10 years of age. Bleeding into lymphangioma can produce sudden proptosis and ecchymosis. Frequently, conjunctival involvement is found.⁴

Rhabdomyosarcoma can usually be differentiated from lymphangioma by MR imaging. Rhabdomyosarcoma characteristically shows a solid homogeneous mass that is isointense to vitreous on T1-weighted images.³ Lymphangioma demonstrates a multicystic mass with lobulated margins, showing hypointensity to vitreous on T1-weighted images and hyperintensity to vitreous on T2-weighted images. The rim of lymphangioma can enhance minimally.⁴ Our case had MR imaging characteristics most consistent with lymphangioma.

Cavitation can occur within other ocular tumors secondary to hemorrhage, necrosis, and mucoid degeneration.⁵ However, cavitation within rhabdomyosarcoma is distinctly unusual. To our knowledge, this finding has not been previously reported. In a review of 250 orbital childhood tumors by Shields and associates,¹ there were no rhabdomyosarcomas with cavitation.

Our case presented a diagnostic dilemma. Rhabdomyosarcoma and lymphangioma occur in similar age groups and are seen with similar clinical findings. The malignant nature of rhabdomyosarcoma vs the benign course of lymphangioma underscores the importance of correct diagnosis. Although conservative management of lymphangioma is generally advised, proper follow-up should be performed.⁶ If the suspected lymphangioma fails to demonstrate resolution or shows progression, biopsy should be considered to rule out rhabdomyosarcoma.

AUTHOR INFORMATION
This study was supported by the Paul Kayser International Award of Merit in Retina Research, Houston, Tex (Dr J. Shields); the Eye Tumor Research Foundation, Philadelphia, Pa (Dr C. Shields); Noel T. and Sara L. Simmons Endowment for Ophthalmic Pathology, Wills Eye Hospital, Philadelphia (Dr Eagle); and the Department of Ophthalmology, Chang Gung Memorial Hospital, Taipei, Taiwan (Dr Chao).

Douglas R. Fetkenhour, BS; Carol L. Shields, MD; An N. Chao, MD; Jerry A. Shields, MD
Philadelphia, Pa

Carl B. Guterman, MD
Hackensack, NJ

Ralph C. Eagle, Jr, MD
Philadelphia

REFERENCES
1. Shields JA, Bakewell B, Augsburger JJ, Donoso LA, Bernardino V. Space-occupying orbital masses in children: a review of 250 consecutive biopsies. Ophthalmology. 1986;93:379-384. ISI | PUBMED 2. Wharam M, Beltangady M, Hays D, et al. Localized orbital rhabdomyosarcoma: an interim report of the Intergroup Rhabdomyosarcoma Study Committee. Ophthalmology. 1987;94:251-254. ISI | PUBMED 3. Shields JA, Shields CL. Myogenic tumors. In: Shields JA, Shields CL, eds. Atlas of Orbital Tumors. Philadelphia, Pa: Lippincott Williams & Wilkins; 1999:106-111. 4. Shields JA, Shields CL. Vascular and hemorrhagic lesions. In: Shields JA, Shields CL, eds. Atlas of Orbital Tumors. Philadelphia, Pa: Lippincott Williams & Wilkins; 1999:60-63. 5. Lois N, Shields CL, Shields JA, Eagle RC, DePotter P. Cavitary melanoma of the ciliary body: a study of eight cases. Ophthalmology. 1998;105:1091-1098. FULL TEXT | ISI | PUBMED 6. Muallem MS, Garzozi HJ. Conservative management of orbital lymphangioma. J Pediatr Ophthalmol Strabismus. 2000;37:41-43. PUBMED

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