Determining if a small melanocytic choroidal lesion is a choroidal melanoma or nevus can be a diagnostic challenge. Documented growth is the most reliable method for determining malignant transformation.¹ The growing “choroidal nevus” may also include a de novo choroidal melanoma initially mislabeled based on its size until continued growth reveals it to be a small choroidal melanoma.² The determination of a de novo choroidal tumor therefore relies solely on the existence of prior fundus photographs.

Because of the absence of routine widefield fundus photography, de novo choroidal melanomas have rarely been reported.^2,3 This article describes a case of a choroidal melanocytic tumor in a White adult diagnosed and treated as a choroidal melanoma based on de novo onset and clinical findings that corroborated growth.

CASE PRESENTATION

A 52-year-old White male without prior ocular history was noted to have a new melanocytic tumor in the left eye without associated symptoms and was referred to the ophthalmic oncology service. The patient’s visual acuity was 20/15 in both eyes. Intraocular pressures were 11 in both eyes, and anterior-segment exam in both eyes and fundus exam in the right eye were unremarkable. In the left eye, a 7.5 mm x 6 mm x 1.2 mm dome-shaped, melanocytic choroidal tumor with overlying orange pigment was observed inferior to the inferotemporal arcade (Figure 1A). Optical coherence tomography over the tumor showed patchy retinal pigment epithelium atrophy with overlying subretinal fluid. B-scan measured a tumor thickness of 1.2 mm (Figures 2A and 2B). The initial diagnosis of the tumor was indeterminate melanocytic tumor (IMT) favoring small choroidal melanoma, given the presence of orange pigment and subretinal fluid.⁴

Review of prior records revealed that yearly exams for the prior 5 years were normal. Most importantly, widefield color fundus photography 4 years prior to presentation showed absence of tumor in the same location as the newly noted choroidal tumor in 2015 (Figure 1B). Of note, the patient did not have ocular melanocytosis or a family history of cancer. Given photographic evidence of a new-onset choroidal melanocytic tumor compared to 4 years prior and the clinical features, the diagnosis of small choroidal melanoma was made. Treatment options were discussed (observation, transpupillary thermotherapy, or plaque brachytherapy) and the patient underwent episcleral plaque brachytherapy (iodine-125, 85 Gy to the apex). Diagnostic and prognostic biopsy of the tumor was deferred given the thinness of the tumor and the risks of adversely affecting vision in an asymptomatic patient. Initial systemic workup, including computed tomography (CT) of the chest, abdomen, and pelvis, were negative for occult malignancy. The tumor demonstrated regression with resolution of subretinal fluid without evidence of radiation retinopathy (Figure 3). Continued systemic surveillance with liver ultrasounds remained negative 5 years after initial diagnosis and his visual acuity remains 20/20 in the left eye without symptoms.

DISCUSSION

There is limited knowledge regarding the onset of choroidal melanocytic tumors, particularly nevogenesis. Population-based studies suggest that active nevogenesis can occur in childhood as documented by new onset choroidal nevus and increasing prevalence in children up to 18 years of age.⁵ The rising prevalence was accounted by photographically documented de novo choroidal nevi in children.⁵ In contrast, there has been only 1 published case of a de novo choroidal nevus in an adult (73 years old).⁶ However, the diagnosis of choroidal nevus in this case remains questionable because the tumor documented had the appearance of reactive retinal pigment epithelium proliferation.

Multiple population-based studies have shown a plateau in the prevalence rate of choroidal nevi in adult populations (≥40 years old). In the Blue Mountains Eye Study there were 3,654 subjects aged 49 to 97 years old located in western Sydney, Australia, with 99% of the population being White.⁷ In a decade-based stratification, no statistically significant association was seen between the prevalence of choroidal nevus and increasing age in patients older than 60 years.⁵ Similar observations have been reproduced in 4 non-White populations of patients over 40 years old in the Singapore Malay Eye Study (SiMES), Multi-Ethnic Study of Atherosclerosis (MESA), Beijing Eye Study (BEI), and National Health and Nutrition Examination Survey (NHANES) (Table 1). In 2 cross-sectional prevalence studies of adult US populations, National Health and Nutrition Survey (NHANES) and Multi-Ethnic Study of Atherosclerosis (MESA), the prevalence of choroidal nevi among White adults, ≥40 years and ≥45 years of age, respectively, did not increase with age (Table 2).

Taken together, population-based studies indicate absence of choroidal nevogenesis in White adults ≥40 years of age, such as the patient described here. Therefore, de novo choroidal melanocytic tumor in an adult is likely to be melanoma rather than nevus. Paucity of such observations can be explained by the lack of widespread routine fundus photography.^2,3 Mislabeling or misclassification of every new small choroidal melanocytic tumor at initial presentation as nevus until continued growth reveals it to be de novo small choroidal melanoma can also explain underreporting of de novo choroidal melnaoma.³ As imaging modalities are adapted into routine eye examinations, more frequent occurrence of de novo choroidal melanoma may be observed than the literature currently reflects.

SUMMARY

In the patient described here, the diagnosis of small choroidal melanoma was made based on photographic evidence of de novo origin in a White adult over 40 years of age and was supported by clinical features, which included the presence of subretinal fluid and orange pigment. The patient was therefore given treatment options rather than continued observation. Following episcleral brachytherapy, the tumor stabilized in size without further growth and remained free of recurrence, metastasis, and radiation retinopathy at 5-year follow-up. On last follow-up visit, the patient’s visual acuity was 20/20 in the affected eye without symptoms.

CONCLUSION

De novo choroidal melanocytic tumors in White adults over 40 years of age should be regarded as choroidal melanoma rather than choroidal nevus, especially when supported by clinical features. It is therefore important to obtain any prior fundus images when presented with a choroidal melanocytic tumor. If such a tumor is unequivocally new on presentation, treatment rather than observation should be considered. RP

REFERENCES

1. Luo S, Raval V, Zabor EC, Singh AD. Small choroidal melanoma: correlation between clinical characteristics and metastatic potential. Ocul Oncol Pathol. 2021;7(6):437-446. doi:10.1159/000519672
2. Sahel JA, Pesavento R, Frederick AR Jr, Albert DM. Melanoma arising de novo over a 16-month period. Arch Ophthalmol. 1988;106(3):381-385. doi:10.1001/archopht.1988.01060130407031
3. Aleksidze N, Medina CA, Singh AD. De novo evolution of a small choroidal melanoma. Ocul Oncol Pathol. 2015;1(2):83-87. doi:10.1159/000368612
4. Singh AD, Grossniklaus HE. What’s in a name? Large choroidal nevus, small choroidal melanoma, or indeterminate melanocytic tumor. Ocul Oncol Pathol. 2021;7(4):235-238. doi:10.1159/000516536
5. Raval V, Bellerive C, Singh AD, Gopinath B, Liew G, Mitchell P. Choroidal nevi in children: prevalence, age of onset, and progression. J AAPOS. 2021;25(4):225.e1-225.e6. doi:10.1016/j.jaapos.2021.03.012
6. Parikh R, Gal-Or O, Sakurada Y, Leong B, Freund KB. Documentation of a new choroidal nevus. Retin Cases Brief Rep. 2021;15(3):202-206. doi:10.1097/ICB.0000000000000822
7. Sumich P, Mitchell P, Wang JJ. Choroidal nevi in a white population: the Blue Mountains Eye Study. Arch Ophthalmol. 1998;116(5):645-650. doi:10.1001/archopht.116.5.645