choroidal melanoma as well as changes in its size, using intrinsic scales. No patterns of fluorescein angiography are pathognomonic for choroidal melanoma.
Although CT and MRI are not widely used in the assessment of uncomplicated intraocular melanocytic tumors, these modalities are useful in identifying tumors in eyes with opaque media and in determining extrascleral extension and involvement of other organs. MRI may be helpful in differentiating atypical vascular lesions from melanocytic tumors.
Differential Diagnosis
The most common lesions that should be considered in the differential diagnosis of posterior uveal melanoma include suspicious choroidal nevi, disciform macular and extramacular lesions, congenital hypertrophy of the RPE (CHRPE), choroidal hemangioma (see Chapter 18), melanocytoma, hemorrhagic detachment of the choroid or RPE, metastatic carcinoma (see Chapter 20) or melanoma, and choroidal osteoma. Table 17-2 offers a more complete list to be considered in cases with amelanotic choroidal masses.
Figure 17-9 Transillumination (TI) of the eye shows the shadow of a choroidal melanoma (decreased TI through the tumor). This technique may be used to mark the tumor base to ensure accurate placement of the radioactive plaque.
Table 17-2
Choroidal nevus has been discussed previously, but it should be reemphasized that no single clinical characteristic is pathognomonic of choroidal melanoma. Diagnostic accuracy is associated with clinical experience and outstanding ancillary testing facilities. Evaluation and management of these complex cases within regional ocular oncology referral centers appears to enhance patient outcome.
Age-related macular degeneration (AMD) may present with extramacular or macular subretinal neovascularization and fibrosis accompanied by varying degrees and patterns of pigmentation. Hemorrhage, a common finding associated with disciform lesions, is not commonly seen with melanomas unless the tumor extends through the Bruch membrane. Clinical evaluation of the fellow eye is important in documenting the presence of degenerative changes in AMD. Fluorescein angiography results are virtually pathognomonic, revealing early hypofluorescence secondary to blockage from the hemorrhage, often followed by late hyperfluorescence in the distribution of the choroidal neovascular membrane. Ultrasonographic testing may reveal increased heterogeneity and a lack of intrinsic vascularity on standardized A-scan. Serial observation will document involutional alterations of the evolving disciform lesion.
CHRPE is a well-defined, flat, darkly pigmented lesion ranging in size from 1 mm to greater than 10 mm in diameter. Patients are asymptomatic, and the lesion is noted during ophthalmic examination, typically in patients in their teens or twenties. In younger patients, CHRPE often appears homogeneously black; in older individuals, foci of depigmentation (lacunae) often develop (Fig 1710). The histology is identical to a condition known as grouped pigmentation of the retina, or bear tracks (Fig 17-11).
The presence of multiple patches of congenital hypertrophy in family members of patients who have Gardner syndrome, a familial polyposis, appears to be a marker for the development of colon carcinoma. Fundus findings enable the ophthalmologist to help the gastroenterologist determine the recommended frequency of colon carcinoma screening in family members (see Chapter 11).
Melanocytoma (magnocellular nevus) of the optic disc typically appears as a dark brown to black epipapillary lesion, often with fibrillar margins as a result of extension into the nerve fiber layer (Fig 17-12; see also Chapter 15, Fig 15-12). It is usually located eccentrically over the optic disc and may be elevated. It is important to differentiate this lesion from melanoma, because a melanocytoma has minimal malignant potential. Studies have shown that about one-third of optic disc melanocytomas have a peripapillary nevus component and that 10% of cases will show minimal but definite growth over a 5-year period. In addition, these lesions can produce an afferent pupillary defect and a variety of visual field abnormalities, ranging from an enlarged blind spot to extensive nerve fiber layer defects.
Figure 17-10 Congenital hypertrophy of the RPE (CHRPE). Examples of varying clinical appearances. A, CHRPE. Note the homogeneous black color and well-defined margins of the nummular lesion. B, Two lesions of CHRPE in the nasal periphery of the fundus. C, D, Color fundus photograph and corresponding fluorescein angiogram of a large CHRPE. Note focal loss of RPE architecture and pigmentation (lacunae) in part C and visible choroidal vasculature in part D. (Part B courtesy of Jacob
Pe’er, MD; parts C and D courtesy of Timothy G. Murray, MD.)
Figure 17-11 Bear tracks. Grouped pigmentation of the retina/RPE represents a forme fruste of CHRPE. Note the distinct bear track configuration (circle) and increased pigmentation.
Suprachoroidal detachments present in 2 forms: hemorrhagic and serous. These lesions are often associated with hypotony and may present in the immediate period after ophthalmic surgery. Clinically, hemorrhagic detachments are often dome-shaped, they involve multiple quadrants, and they are associated with breakthrough vitreous bleeding. A- and B-scan ultrasonography readings may closely resemble those of melanoma but show an absence of intrinsic vascularity and an evolution of the hemorrhage over time. Observational management is indicated in most cases. MRI with gadolinium enhancement may be of benefit in selected cases to document characteristic alterations.
Figure 17-12 Melanocytoma of the optic disc. Note varying clinical appearance in these 2 examples based on degree of choroidal pigmentation: lesion in (A) darkly pigmented fundus and (B) lightly pigmented fundus. (Part B courtesy of Timothy G.
Murray, MD.)
Choroidal osteomas are benign bony tumors that typically arise from the juxtapapillary choroid in adolescent to young adult patients (more commonly in women than men) and are bilateral in 20%– 25% of cases. The characteristic lesion appears yellow to orange, and it has well-defined margins (Fig 17-13). Ultrasonography reveals a high-amplitude echo corresponding to the plate of bone and loss of the normal orbital echoes behind the lesion. These tumors can also be seen on CT; their hallmark is calcification. Choroidal osteomas typically enlarge slowly over many years. If these lesions involve the macula, vision is generally impaired. Subretinal neovascularization is a common complication of macular choroidal osteomas. The etiology of these lesions is unknown, but chronic low-grade choroidal inflammation has been suspected in some cases (see Chapter 12).