A Chance Finding of Pigmented Retinal Spots

Kathryn A. Camero, MD; Kimberly G. Yen, MD

Disclosures

September 25, 2015

Discussion

CHRPE is a benign pigmented lesion that often raises suspicion for malignant choroidal melanoma.

First described by Buettner in 1974, CHRPE appears as a flat, pigmented, well-demarcated lesion located at level of the RPE.[1,2,3,4] The lesions range in size from < 1 disc diameter to 14 disc diameters,[3] and the average lesion is > 50% thicker than normal surrounding retinal pigment epithelium.[5] Lesions differ by the quality of the margins (smooth vs scalloped) and amount and type of pigmentation.[3] The pigment ranges from gray to brown and black, and the lesions are surrounded by characteristic pigmented or nonpigmented halos.[4,6] Common pigment variations include peripheral marginal halos, orange mottling, peripheral mottling, and "Swiss cheese" hypopigmented areas.[3]

Patients often present with normal visual acuity and full visual fields, although some scotoma and field defects have been documented depending on location and technology used. Optical coherence tomography reveals retinal thinning over the area of CHRPE as well as loss of the photoreceptor layer, corresponding to the related visual field defects observed.[5]Histologically, the lesions show pigment granule hypertrophy with hypopigmented RPE at the margins to give the characteristic halo.[6]

It is important to differentiate CHPRE from choroidal melanoma and nevi. Scanning laser ophthalmoscopes can be used to distinguish between the two conditions; in the case of nevi, the choroid appears darker compared with the superficial retina.[7] The orange mottling of CHRPE can appear similar to the orange lipofuscin deposits of malignant melanoma but can be distinguished because melanomas do not transmit light and prevent early choroidal fluorescence.[3]

Through serial retinal photographic examinations, studies show that 46% of CHRPE lesions enlarge over time, with a median rate of enlargement of 2 µ/mm lesion base per month.[4] Lacunae enlarge in 40% of CHRPE cases, and the relative size of lacunae to the entire CHRPE lesion is the most significant factor associated with enlargement. The reason for enlargement is unclear, but some theories include the loss of contact inhibition from neighboring cells[8] and the proliferation of atrophic, hypertrophic, or hyperplasic cells[9] to make up for the normal thinning of the RPE with time.

Although CHRPE is considered to be a benign lesion, rare cases of primary malignant adenocarcinoma of the RPE have been documented.[4,10,11] These nodular lesions are typically unilateral, unifocal, and located at the equator. The CHRPE lesions from which they originated were often significantly larger with patchy areas of lacunae formation and depigmentation.[11]

CHRPE-like lesions also have been associated with such colon cancer syndromes as familial adenomatous polyposis (FAP). Both CHRPE and CHRPE-like lesions in FAP appear as flat, pigmented lesions with lacunae and surrounding halo; however, FAP-associated lesions are multiple, bilateral, and found in a pisciform arrangement.[4,12,13] One study found that CHRPE lesions in patients with FAP were characteristically bilateral with depigmented halos.[14] CHRPE lesions that might be associated with FAP are characterized by the presence of four separate lesions or two lesions, with one being larger than half of the optic disc diameter.[15,16] It is recommended that individuals meeting the above criteria obtain annual sigmoidoscopy starting before age 10 years to monitor polyp development, especially in the setting of known FAP.[15,17] No CHRPE lesions are expressed in 20%-30% of patients with FAP; therefore, retinal exams cannot conclusively rule out FAP in families with CHRPE-negative status.[16,18] For families with CHRPE-positive status, the presence of CHRPE lesions has a 100% positive predictive value and can be useful in early diagnosis.[17] However, ophthalmic exam should be used in conjunction with mutation analysis and endoscopy because mutation analysis is the only test with 100% certainty in ruling out disease.[18]

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