Teaching Case

A 58-year-old male patient presented with left sided progressive loss of vision over the last one year. Ophthalmologic examination could not be helpful to put the diagnosis because of the vitreous hemorrhage.

A 58-year-old male patient presented with left sided progressive loss of vision over the last one year. Ophthalmoscopic examination could not be helpful to put the diagnosis because of the vitreous hemorrhage. MRI study of the orbits with spin-echo T1-weighted, fast spin-echo T2-weighted sequences on three orthogonal planes was performed on a 1.5 T MR scanner. An intraglobal mass lesion was detected at the posterior part of the left globe, with distinctive signal intensity characteristics, hyperintense on T1, and hypointense on T2-weighted sequences, leading to the diagnosis of “choroidal melanocytic malignant melanoma” The globe was totally excised following MRI study of the patient. The histopathologic diagnosis was the same as the radiological diagnosis.

Uveal malignant melanoma is the most common primary intraocular neoplasm in adult patients. It is most commonly detected between the ages 50 to 70 years old. The choroid is the most common location ( 85-93 %), followed by ciliary body (4-9 %), and by iris (3-6 %). Although most of the tumors are melanotic, some of the tumors may be amelanotic. The tumor initially grows flat within the choroid, and later on elevates Bruch’s membrane, leading to the rupture of membrane, and it assumes the characteristic mushroom shape growing towards the vitreous cavity. The retina over the surface of tumor becomes elevated and detached. Uveal melanoma is almost always unilateral. Choroidal lesions elevated more than 3 mm are usually well visualized on MRI studies, whereas lesions less than 3 mm are better studied with sonography. Sonography usually reveals a small flat hyperechoic solid mass. Computed tomography shows ill defined hyperdense thickening of wall of globe with inward bulging. MRI pictures show variability, but the most common pattern is sharply circumscribed hyperintense lesion on T1 weighted images and hypointense lesion on T2 weighted images in melanocytic type due to paramagnetic properties of melanin pigment. However the opposite signal intensity characteristics may be seen in amelanocytic type, and contrast enhancement is an additional finding in this subtype of lesions. There are additional MRI findings related to retinal detachment and vitreous hemorrhage as well. Invasion of the sclera, extension of tumor in the optic disc, Tenon’s capsule, and extraocular invasion can be easily detected by MRI studies. Uveal melanoma metastases are commonly seen to liver, lung, bone, kidney, and brain. The differential diagnosis involves a few benign and malignant uveal melanomas. The main ocular lesions simulating uveal melanoma are choroidal hematoma, metastases, choroidal hemangioma, choroidal detachment, choroidal nevi. These conditions should be ruled out by MRI findings, and ophthalmoscopic examination, clinical history of the patient.