Flat choroidal melanoma masquerading as central serous chorioretinopathy.

There are several mimickers of choroidal melanoma. We report a patient with recent family stress who developed blurred vision to 20/50 OD and was found to have unilateral central serous chorioretinopathy and a coincidental choroidal nevus. After 1 year without resolution of the subretinal fluid, the patient was referred for our opinion. On examination, visual acuity was 20/50 in the right eye and 20/20 in the left eye. The left eye was normal. Evaluation of the right eye showed a small, pigmented submacular choroidal lesion measuring 4 mm × 3 mm. Ultrasonography documented an isoechoic mass measuring 1.71 mm in thickness. Optical coherence tomography showed subretinal fluid with shaggy photoreceptors and hyper-reflective material within the subretinal fluid, likely indicative of lipofuscin within macrophages. Autofluorescence revealed orange pigment overlying the lesion. These features were strongly suggestive of small choroidal melanoma with five risk factors for tumor growth. Treatment with Iodine-125 plaque brachytherapy was performed on the patient. The readers should keep in mind that choroidal melanoma can manifest as a tiny choroidal mass with related multimodal imaging features of subretinal fluid and orange pigment.

Introduction

There are several benign and malignant fundus conditions that can mislead the clinician in the detection of small choroidal melanoma.[1] This is because choroidal melanoma is unusually rare and can present with nonspecific symptoms of blurred vision, flashes, floaters, and metamorphopsia, features that might be seen with more common conditions such as age-related macular degeneration and central serous chorioretinopathy (CSCR).[1]

One difficulty is that choroidal melanoma can be mistaken as an “innocent bystander” choroidal nevus in a patient suspected with a more common condition. This is particularly prevalent with CSCR, in which serous retinal detachment in a middle-age patient is attributed to that benign condition, and an adjacent pigmented lesion is labeled nevus. In such cases, choroidal melanoma can be overlooked or hidden underneath serous fluid. To reduce mistaken diagnosis, we have identified clinical risk factors for differentiating choroidal nevus from melanoma, represented by the mnemonic “TFSOM” for “To Find Small Ocular Melanoma.” These factors include thickness greater than 2 mm, subretinal fluid, visual symptoms, overlying orange pigment, and tumor margin within 3 mm of the optic disc.[1]

Patients with three or more findings have a 5-year risk for tumor growth in over 50% of the cases; early intervention is advised for the best prognosis. Further diagnostic measures for melanoma detection using enhanced depth imaging-optical coherence tomography (EDI-OCT) can assist in tumor identification and avoid misdiagnosis. Tumor detection at its earliest point is critical for maximizing the prognosis.[23] Herein, we describe a patient with presumed CSCR who was found to have an underlying small choroidal melanoma that responded to plaque radiotherapy.

Case Report

A 49-year-old caucasian male was referred for evaluation of a pigmented choroidal lesion after reporting blurred vision for 6 months. He had an 8-year history of choroidal nevus in the right macula. The patient had recently undergone a divorce and subsequent job loss. The blurred vision began shortly thereafter and was attributed to CSCR related to stress. The patient was referred to our service when the subretinal fluid did not resolve after 6 months.

On examination, visual acuity was 20/50 in the right eye (OD) and 20/20 in the left eye (OS). Intraocular pressures were 19 mmHg in the OD and 15 mmHg in the OS, with the anterior segment unremarkable in both eyes (OU). Fundus examination of the OS was normal.

Fundus examination of the OD showed a small, pigmented submacular choroidal lesion measuring 4 mm × 3 mm. Orange pigment was noted overlying the lesion clinically and was hyperautofluorescent [Figure 1]. Drusen were absent. Ultrasound revealed an isoechoic mass measuring 1.71 mm in thickness. EDI-OCT documented subretinal fluid with shaggy photoreceptors and hyper-reflective material within the subretinal fluid, likely indicative of lipofuscin within macrophages [Figure 2]. EDI-OCT measurement of the subfoveal choroidal thickness adjacent to the lesion in the affected eye was 390 microns, compared to the subfoveal choroidal thickness in the fellow eye of 279 microns.

Figure 1

(a) The right fundus showed a small pigmented submacular mass with prominent overlying orange pigment and shallow subretinal fluid, consistent with small choroidal melanoma. (b) Autofluorescence photography documenting hyperautofluorescence of overlying lipofuscin. (c) Spectral domain optical coherence tomography showing subfoveal fluid with shaggy photoreceptors and a deep, minimally elevated, poorly-defined, choroidal mass compressing the choroidal vasculature

Figure 2

Optical coherence tomography images through the tumor showing choroidal infiltration with obliteration of choroidal vascular markings and posterior shadowing of choroidal details. The extent of the pigmented lesion is marked with yellow arrows on each image

When assessing risk factors for small choroidal melanoma, this patient exhibited five of eight including subretinal fluid, orange pigment, margin within 3 mm of the disc, symptoms, and absence of halo and drusen.[4] A melanocytic lesion with these factors carries an approximate risk >50% for growth into melanoma within 5 years.[45] The patient was informed regarding this risk and given options of observation versus radiotherapy. Iodine-125 plaque brachytherapy was provided, and he was custom-fit with a radioactive plaque to give a radiation dose of 70 gray to the tumor apex.

Discussion

There are several mimickers of choroidal melanoma that create elements of diagnostic uncertainty.[1] A review of 12,000 patients referred for possible choroidal melanoma at a tertiary referral center over a 25-year time period revealed 1739 patients (14%) with pseudomelanoma.[1] In that series, the leading pseudomelanomas included choroidal nevus (49%), peripheral exudative hemorrhagic chorioretinopathy (8%), congenital hypertrophy of the retinal pigment epithelium (6%), and several other conditions.

In this case, the subretinal fluid was initially suspected to represent CSCR as there was recent personal stress. CSCR is characterized commonly by unilateral or bilateral visual loss from subretinal fluid or retinal pigment epithelial detachment. This disease typically manifests in young adult males under high stress,[6] as in our patient, and can be exacerbated by steroid use.[7] The subretinal fluid, however, typically resolves spontaneously over several months.[7] In our case, fluid persisted for 6 months, prompting concern that fluid was related to the pigmented lesion. Further, bilateral uniform increase choroidal thickness on EDI-OCT, a feature of CSCR, was lacking as the fellow eye had normal thickness and the involved eye showed only focal increased thickness at the tumor site.

EDI-OCT is an important tool for the differentiation of choroidal nevus from choroidal melanoma. In an analysis of 37 eyes with small choroidal melanoma, Shields et al. found that melanoma classically displays features of subretinal fluid (92%), subretinal lipofuscin (95%), shaggy photoreceptors (49%), absence of photoreceptors (24%), absence of the inner segment-outer segment junction (65%), absence of the external limiting membrane (43%), irregularity of the inner plexiform layer (8%), and irregularity of the ganglion cell layer (8%) on EDI-OCT. Most small choroidal melanomas are characterized by a dome-shaped, smooth contour, and with relatively fresh subretinal fluid demonstrating shaggy photoreceptors and subretinal lipofusin. By contrast, choroidal nevus classically displays no subretinal fluid (84%), absence of subretinal lipofuscin (55%), completely retracted “nonshaggy” photoreceptors (43%), normal inner segment-outer segment junction (57%), normal external limiting membrane (80%), normal inner plexiform layer (100%), and normal ganglion cell layer (100%).[8] A comparative analysis of nevus versus melanoma revealed three statistically important features for differentiation including fresh subretinal fluid with subretinal lipofuscin deposits and shaggy photoreceptors with small melanoma.[9] While EDI-OCT may not be absolutely diagnostic in the differentiation of choroidal nevus from melanoma, it can provide helpful clues.

In summary, we report the early detection of small choroidal melanoma that simulated nonresolving CSCR. Early detection of melanoma is critical for life prognosis. Both Damato et al.[10] and Shields et al.[9] show that metastatic risk is minimized when melanoma is detected at its earliest, thinnest point.

Financial support and sponsorship

Eye Tumor Research Foundation, Philadelphia, PA (CLS).

Conflicts of interest

There are no conflicts of interest.