MR Imaging Findings of Uveal Leiomyoma: Three Cases

Discussion

The appropriate clinical diagnosis determined by using various diagnostic tools in ophthalmology does not always require further imaging studies, including CT or MR imaging, particularly for intraocular lesions. CT or MR imaging may help in the diagnosis or management of an intraocular disease when the opaque ocular media precludes a clear view or when vitreous hemorrhage and subretinal effusion obscure ophthalmoscopic viewing. Recognizing the intraocular lesion as melanoma is important with its invasiveness, because it determines whether a treatment plan such as local globe maintenance therapies (local excision, brachytheraphy, or percutaneous irradiation) or radical therapies (enucleation or exenteration) should be used for a uveal mass (1). But other uveal tumors cannot be readily differentiated from uveal melanoma, especially amelanotic tumors, even if they are rare or less common in incidence (2).

Clinically, UTLs are difficult to differentiate from amelanotic uveal malignant melanomas, which are revealed as protuberant masses on ophthalmoscopic examination (3). In a few case series, however, some clinical and pathologic characteristics have been reported that might serve to differentiate UTLs from melanomas (3, 4). UTLs tend to occur in younger patients and also have a predilection for female patients. They affect the ciliary body and peripheral choroids, rather than the posterior choroid, and involve the supraciliary or suprachoroidal space in terms of location of the globe wall stratification. By contrast, uveal melanomas are less likely to occur in the peripheral choroid or ciliary body and involve the uveal stroma in the globe wall (5). On transillumination, UTLs usually transmit light readily, whereas most melanomas cast a shadow (4). In our three cases, two patients were female and age ranged between 20 and 39 years. In all three cases, the UTL was located in the ciliochoroidal region, was protuberant in shape, and was isointense to brain on both T1- and T2-weighted sequences. UTLs were strongly enhanced with gadolinium injection. These MR imaging features and the location of the UTL may reduce the number of the differential diagnoses, in that 1) choroidal metastasis is usually seen with diffuse outline in shape in the choroid posterior to the equator of the globe (6); 2) choroidal hemangioma in a solitary circumscribed form is reddish orange on ophthalmoscopic examination, is mainly located in the posterior choroids (6), and is hyperintense on fast spin-echo T2-weighted images relative to vitreous matter (7); 3) uveal nevus is the most frequently seen in the posterior third of the choroid, is flat in shape, and is for the most part <5 mm in basal diameter (8); 4) melanocytoma is deeply pigmented on fundoscopic examination and usually occurs at the optic disk (9); and 5) choroidal osteoma appears as a platelike calcified thickening of the posterior choroid, typically in the juxtapapillary region (10). Nevertheless, other uveal tumors—including schwannoma, neurofibroma, medulloepithelioma, or even amelanotic melanoma—cannot be differentiated from UTL even by both clinical and imaging examinations.

Conclusion

UTL tends to occur in the ciliochoroidal region and to appear as a protuberant mass that is isointense to brain on T1- and T2-weighted MR images. UTL should, therefore, be included in the differential diagnosis when a protuberant mass that is isointense to brain is seen in the ciliochoroidal region.