Incidence of iris melanoma in western Norway

An optimized 3T MRI scan protocol to assess iris melanoma with subsequent histopathological verification - A prospective study

INTRODUCTION

Magnetic resonance imaging (MRI) has demonstrated high levels of tissue contrast, accuracy and reproducibility in evaluating posterior uveal melanoma. Owing to smaller size, the role of MRI in detecting and characterising iris melanoma has not yet been explored.

AIMS

To develop a protocol to image iris melanoma and describe the MRI characteristics of histopathological-confirmed iris melanoma.

MATERIALS AND METHODS

An optimised MRI protocol, using a 3T MRI scanner and a 32-channel head coil, was developed to image iris tumours. A prospective, single-centre, 12-month study was conducted on all patients with lesions suspicious for iris melanoma. All patients were offered an MRI scan in addition to the standardised clinical procedures. Image quality comparison was made with existing clinical investigations. Iris melanoma characteristics on MRI are described.

RESULTS

A successful optimised MRI scan protocol was developed that was able to detect and characterise iris melanoma. One normal participant and five patients with subsequent histopathological-confirmed iris melanoma (n = 6) were recruited. Four patients completed the full MRI sequence. All iris melanoma were detected on at least one T1- or T2-weighted images. When compared to the vitreous, all iris melanomas demonstrated hyper-intensity on T1-weighted images and hypo-intensity on T2-weighted images. On T1-mapping, T1-values of iris melanoma demonstrated an inverse relationship with the degree of tumour pigmentation.

CONCLUSIONS

This study highlights an optimised, easily reproducible MRI scan protocol to image iris melanoma. Numerous MR imaging characteristics of iris melanoma are reported for the first time and a potential non-invasive tumour biomarker is described.

Iris melanoma: Review of clinical features, risks, management, and outcomes

Primary uveal melanoma is rare and affects approximately 8,000 persons per year worldwide. This malignancy can involve the iris, ciliary body, and choroid. Of these three structures, the iris is the least commonly affected site, representing only 4% of all uveal melanomas. Iris melanoma can arise from iris melanocytic nevus, iris melanocytosis, or de novo. In a longitudinal study of 1,611 patients with iris nevus, transformation into melanoma, using Kaplan-Meier estimates, was found in 2.6% by five years and in 4.1% by 10 years. The factors that predicted growth of iris melanocytic nevus into melanoma are denoted by a letter (ABCDEF) guide: A for age ≤40 years old at presentation (hazard ratio [HR] = 3, P = .01), B for blood (hyphema) (HR = 9, P < .0004), C for clock hour of tumor inferiorly (tumor location) (HR = 9, P = .03), D for diffuse flat tumor configuration (HR = 14, P = .02), E for ectropion uveae (HR = 4, P = .002), and F for feathery ill-defined margins (HR = 3, P = .02). At diagnosis, iris melanoma has a mean cross-sectional diameter of 5.5 mm and thickness of 2.1 mm, often with tumor seeding (28%) and secondary glaucoma (35%). We provide a comprehensive review of iris nevus and melanoma to explore relevant demographic and clinical data, risk factors for tumor growth, management, and prognosis, with the hope that clinicians will be more comfortable in understanding this rare malignant condition.

Topography and clinical features of iris melanoma

BACKGROUND

To characterise the topographical and clinical features of primary iris melanoma and to visualise the patterns of tumour extent in the iris.

METHODS

Clinical characteristics of iris melanomas were analysed, and data on their size, shape, and location were converted into a database of two-dimensional iris charts by means of computer-drawing software. The geometric centre of each tumour was entered into corresponding sectors of the chart. The extent of the melanomas was computationally visualised by merging the iris drawings and displaying the number of overlapping tumours on colour-coded iris maps.

RESULTS

Twenty-nine patients (18 females and 11 males) with a mean age of 52 years met the inclusion criteria. The mean largest tumour diameter was 6.1 mm (range, 1.8-11.0 mm). Five tumours (17%) involved the pupillary margin, 10 (34%) involved the iris root, and 10 (34%) involved both sites. The hemispheric location of the tumour centroid was superior in 3 eyes (11%) and inferior in 25 (89%) (p < 0.0001), and the distribution between the temporal and nasal hemispheres was 17 (61%) and 11 (39%), respectively (p = 0.26). In females, the iris melanomas were located more temporally (p  =  0.02) and had more often originated from a pre-existing naevus (p = 0.03), than in males. There was also shift towards more temporally located melanomas in younger patients.

CONCLUSIONS

The lower temporal iris quadrant is the preferential area of melanoma occurrence and growth. Iris melanoma tends to be more temporally located in females, who compared with males also have a higher proportion of melanomas arising from a pre-existing naevus.

Iris Melanoma: Management and Prognosis

Iris melanomas represent 2–5% of uveal melanomas. Iris melanomas vary in their size, shape, degree of pigmentation and clinical behavior. The main local clinical complications of iris melanomas are tumor vascularization, ectropion uvea, pupillary distortion, pigment dispersion, sector cataract, chronic uveitis, hyphema and glaucoma with irreversible optic nerve damage. The most effective treatment for iris nevus and melanoma remains debatable; treatment modalities have been proposed depending on the local status as well as the age and general condition of the patient. A melanocytic iris nevus is usually observed until documented progression is identified. In this case, radiotherapy or surgical resection is generally performed. Cataract, glaucoma and limbal stem cell deficiency are usually secondary to radiotherapy, while incomplete tumor excisions, which could lead to recurrence, hemorrhage, vitreous loss, dislocated lens, iridocyclitis, macular edema, retinal detachment, glaucoma and cataract, are related to surgical resection. In some cases, a combination of radiotherapy and surgery is used. Conservative treatment is an efficient alternative to enucleation and allows good local tumor control.

Iris Colour and the Risk of Developing Uveal Melanoma

Uveal melanoma (UM) is a global disease which especially occurs in elderly people. Its incidence varies widely between populations, with the highest incidence among Caucasians, and a South-to-North increase in Europe. As northern Europeans often have blond hair and light eyes, we wondered whether iris colour may be a predisposing factor for UM and if so, why. We compared the distribution of iris colour between Dutch UM patients and healthy Dutch controls, using data from the Rotterdam Study (RS), and reviewed the literature regarding iris colour. We describe molecular mechanisms that might explain the observed associations. When comparing a group of Dutch UM patients with controls, we observed that individuals from Caucasian ancestry with a green/hazel iris colour (Odds Ratio (OR) = 3.64, 95% Confidence Interval (CI) 2.57-5.14) and individuals with a blue/grey iris colour (OR = 1.38, 95% CI 1.04-1.82) had a significantly higher crude risk of UM than those with brown eyes. According to the literature, this may be due to a difference in the function of pheomelanin (associated with a light iris colour) and eumelanin (associated with a brown iris colour). The combination of light-induced stress and aging may affect pheomelanin-carrying melanocytes in a different way than eumelanin-carrying melanocytes, increasing the risk of developing a malignancy.

Iris nevus growth into melanoma: analysis of 1611 consecutive eyes: the ABCDEF guide

PURPOSE

To determine clinical features predictive of growth of iris nevus into melanoma.

DESIGN

Retrospective, comparative case series.

PARTICIPANTS

A total of 1611 consecutive patients referred to an ocular oncology center with iris nevus.

INTERVENTION

Observation and photographic documentation.

MAIN OUTCOME MEASURES

Growth into melanoma.

RESULTS

The mean age at referral for iris nevus was 51 years (median, 54; range, <1-94 years). At presentation, the mean tumor basal diameter was 3 mm (median, 3 mm; range, <1-12 mm) and mean tumor thickness was 0.8 mm (median, 0.5 mm; range, 0-5 mm). All patients were initially diagnosed with benign iris nevus. Growth of iris nevus to melanoma was confirmed in 2% of eyes (n = 27) over a mean follow-up of 68 months (median, 46 months; range, 3-465 months). By Kaplan-Meier estimates, iris nevus growth to melanoma occurred in <1%, 3%, 4%, 8%, and 11% at 1, 5, 10, 15, and 20 years, respectively. Factors predictive of iris nevus growth to melanoma by multivariable analysis included age ≤ 40 years at presentation (hazard ratio [HR], 3), episode of hyphema (HR, 9), 4:00 to 9:00 clock hour location of tumor (HR, 9), diffuse tumor (involving entire iris surface) (HR, 14), ectropion uveae (HR, 4), and feathery tumor margins (HR, 3). Additional important factors by univariable analysis included tumor seeding on the iris or in the anterior chamber angle, feeder vessels, and nodule formation. These factors can be remembered using the mnemonic ABCDEF, representing A = age young, B = blood, C = clock hour inferior, D = diffuse, E = ectropion, and F = feathery margin.

CONCLUSIONS

In an analysis of 1611 cases of iris nevus referred for evaluation at an ocular oncology center, growth into melanoma occurred in 8% by 15 years. Risk factors for growth, identified by ABCDEF included Age young, Blood (hyphema), Clock hour inferior, Diffuse configuration, Ectropion uveae, and Feathery tumor margin.

Iris melanoma: features and prognosis in 317 children and adults

PURPOSE

To evaluate iris melanoma in children versus adults.

METHODS

Retrospective, nonrandomized clinical case series including all patients with a clinical diagnosis of iris melanoma managed at the Ocular Oncology Service at Wills Eye Institute over 40 years. Patients were divided into three age categories based on age at presentation: children (≤ 20 years), mid-adults (21-60 years), and older adults (>60 years). The clinical features, treatments, and outcomes were statistically analyzed based on patient age at presentation. The main outcome measures were melanoma features and related metastasis and death.

RESULTS

Of 8,101 eyes with uveal melanoma, there were 317 (4%) with iris melanoma, including 24 (8%) children (≤ 20 years), 187 (59%) mid-adults (21-60 years), and 106 (33%) older adults (>60 years). There was no age-related difference in race, sex, tumor quadrant, thickness, pigmentation, associated corectopia, ectropion uveae, hyphema, or extraocular extension. Significant age-related differences were found with mean tumor basal diameter, tapioca appearance, mean intraocular pressure, secondary glaucoma, tumor seeding in angle, and mean number of clock hours of angle seeding. Multivariate analysis of factors predictive of metastasis included extraocular extension and high intraocular pressure. Factors predictive of death included increased tumor thickness and high intraocular pressure. There was no difference in metastasis or death by age group.

CONCLUSIONS

Iris melanoma shows significant clinical differences in children versus adults, with smaller tumor size, less tumor seeding in angle, and lower incidence of secondary glaucoma. There was no significant difference in metastasis or death by age group.