An Eye for an Eye
[Jan 2023]

A 37-year-old patient was referred to our Imaging Department following an ophthalmic exam, which revealed 2 pigmented left iris lesions, suspicious for melanoma with possible ciliary body involvement (Fig. 1) but required an ultrasound for further evaluation. These were previously flagged to the Ophthalmologist by an Optometrist, who was concerned by an abnormal area of pigmentation of the left iris.

The patient himself had noticed it relatively long before that, but as he had not experienced any other symptoms, he only became concerned when the lesion increased in size.

A high resolution ultrasound examination of both orbits was performed with the use of a linear array 18 MHz probe.Examination of the left globe revealed a 5 mm mass of the iris extending antero-laterally and involving the inferior ciliary body and suspensory ligaments of the left eye (Video 1). It was in close proximity to the lens, protruding both into the anterior and posterior chambers (Fig. 2). Superb microvascular imaging (SMI) demonstrated minimal flow within the lesion (Fig. 3). Despite the mention of 2 pigmented lesions, there was no other lesion seen on ultrasound. Examination on the contralateral side was normal.
Incidentally, the patient had had a computed tomography (CT) scan of the head (owing to unrelated, neurological symptoms) a few months prior to his presentation to the Ophthalmologist. In retrospect, the left globe lesion was just visible, but CT provided an inferior level of detail which was not diagnostic, in contradistinction to the superior anatomical detail delineated on ultrasound (Fig. 4).

Clinical assessment supported by the imaging findings led to the diagnosis of a uveal melanoma.

BACKGROUND:
Uveal melanoma (UM), being the most common primary intraocular tumour in adults, is an important pathology that needs to be considered when undertaking ultrasound examination of the orbit.

CLINICAL PERSPECTIVE:
Sonographic assessment of UM has been well-established, and it is classically described as hyperechoic, dome-shaped lesion demonstrating acoustic hollowness and unlike benign lesion typically has some vascular flow. Subretinal fluid may also be present.
Certain imaging features that can be easily evaluated on ultrasound play central role in primary tumour (T) classification (e.g. thickness, largest basal diameter, involvement of ciliary body or extrascleral extension)(1).

Another notable contribution of ultrasound to the multimodal ocular oncology assessment is the ability to help distinguish UM from its most important differential: a choroidal nevus (benign pigmented lesion). As established by CL. Shields et al. on a retrospective review of 3806 consecutive choroidal nevi imaging cases, multimodal imaging can capture risk factors for malignant transformation of the nevus (2). These include lesion thickness >2mm and melanoma hollowness (low internal reflectivity), which is best evaluated on US.

There are other strengths that are unique for US among other diagnostic imaging modalities in the evaluation of intraocular tumours. These include superb spatial resolution, which allows for precise visualisation of fine intraocular structures. In addition, the latest advances in microflow imaging enable detection of small vessels and detailed characterisation of the tumour. As seen in our case, US can provide much more diagnostic information than CT and in some instances even MRI.

THERAPY PLANNING:
With the advent of novel, eye-conserving treatment options and individualised therapeutic modalities, the information ultrasound provides on tumour morphology is of great value to the Ophthalmologist.

It is worth noting that the value of US in patients suffering from UM is not limited to the primary tumour, which metastasizes most commonly to the liver. While older literature suggested that hepatic ultrasound had poor sensitivity in detecting liver metastases in UM, more recent studies found its high value in surveillance of the patients affected by this malignancy (3). MM. Choudhary et al. concluded that surveillance based on serial hepatic US scans and confirmatory imaging as needed offers high likelihood of detecting asymptomatic liver metastases in UM patients.

This highlights the importance of sonography, not only in the primary tumour evaluation, but also in the follow-up phase.

OUTCOME & PROGNOSIS:
Unfortunately, owing to the extent of tumour invasion it was decided that radical surgery would be the best treatment option and thus our patient underwent complete enucleation of the left globe.

Despite the aforementioned advances in treatment options, around half of the patients with uveal melanoma develop metastatic disease 10-15 years after initial diagnosis, which often leads to a fatal outcome.

- Ocular ultrasound is the primary test used in confirming uveal melanoma diagnosis and its classification, which guides the decision on the most appropriate therapeutic approach.

- In certain instances, it can provide more diagnostic value than other cross-sectional imaging and it remains useful in the surveillance of UM patients.

1) Fallico M, Raciti G, Longo A, et al. Current molecular and clinical insights into uveal melanoma (Review). Int J Oncol. 2021;58(4):10.

2) Shields CL, Dalvin LA, Ancona-Lezama D, et al. Choroidal nevus imaging features in 3,806 cases and risk factors for transformation into melanoma in 2,355 cases: The 2020 Taylor R. Smith and Victor T. Curtin lecture. Retina. 2019;39(10):1840-1851.

3) Choudhary MM, Gupta A, Bena J, Emch T, Singh AD. Hepatic ultrasonography for surveillance in patients with uveal melanoma. JAMA Ophthalmol. 2016;134(2):174-180.