Clinical Evaluation of Choroidal Melanoma

From EyeWiki



Disease Entity

Choroidal melanoma is the second most common intraocular tumor – metastasis being the most frequent – and the most common primary intraocular malignancy in the adult population. It arises from malignant uveal melanocytes. Posterior uveal melanoma, as it is also known, has distinct clinical characteristics that facilitate its differentiation from other pigmented and non-pigmented lesions of the choroid. 


Symptoms

Symptoms are not a common initial presentation of small melanomas, but can be present in larger lesions and melanomas that affect central macula. The main symptoms are decreased visual acuity, visual field defects (scotomas), flashes and floaters. The presence of symptoms is more commonly found in melanomas than in choroidal nevi.

Clinical diagnosis

Posterior uveal melanomas typically present as an elevated domed-shaped gray lesion of the choroid with irregular margins not sharply demarcated. When the melanoma breaks the Brüch’s membrane it acquires a mushroom-shaped configuration.

Several clinical characteristics should be looked for in the clinical evaluation of a suspicious lesion:

  • Color: Grayish lesion located deep down in the choroid, retinal vessels are evident overlying the lesion. However, there are also amelanotic tumors with a yellowish appearance.
  • Thickness: choroidal melanomas tend to be lesions more than 2 mm thick. In contrast, choroidal nevi – the main differential diagnosis – are more likely to present as flat or slightly elevated masses.
  • Subretinal fluid: The presence of exudative detachment of the neurosensory retina or the retinal pigment epithelium (RPE) is common.
  • Orange pigment: Lipofuscin accumulation in the RPE overlying choroidal melanomas is a frequent finding.
  • Sentinel vessel: A tortuous and dilated episcleral vessel is visible in the episclera above a melanoma.
  • Secondary glaucoma: Secondary angle closure glaucoma can develop due to anterior displacement of the iris-lens diaphragm by the mass.


The size of choroidal melanomas is one of the most important clinical characteristics. Size is used to classify these tumors, according to the criteria of the Collaborative Ocular Melanoma Study (COMS). This study classified melanomas using largest basal dimension and apical height in three groups: small, medium and large melanomas. Treatment strategies vary depending on this classification.

Apical height Largest basal diameter
Small 1.0 - 3.0 mm 5.0 - 16.0 mm
Medium 2.5 - 10 mm less than 16 mm
Large more than 10 mm more than 16 mm + no mets

Diagnostic procedures

Additional ancillary tests can aid in the clinical evaluation of a melanoma:

Ultrasound

This is a helpful diagnostic test that helps in determining thickness (apical height), extraocular extension (such as scleral nodules), and also aids in growth documentation during the follow up of a suspicious nevus/small melanoma.

  • A-mode: Posterior uveal melanomas show medium to low internal reflectivity.
  • B-mode: Domed or mushroom-shaped mass characterized by an acoustically silent zone within the tumor (ultrasonographic hollowness).  Subretinal fluid can also be commonly seen on the margins of the lesion.


Color Doppler ultrasound

Choroidal melanomas show pulsatile blood flow at the tumor base. This finding is not found in nevi.

Fluorescein and indocyanin green angiography (ICGA)

  • Hypofluorescence: Due to blockage of the choroidal blood flow by the pigmentation inherent to the tumor.
  • Hyperfluorescence: Small hyperfluorescent spots may be seen due to lipofuscin deposition at the RPE level.
  • Circulation:“Double circulation” pattern consisting of an internal circulation within the lesion and the normal vascularity of the overlying retina. This characteristic is more evident in ICGA

Fundus autoflorescence

Orange lipofuscin pigmentation possesses autofluorescent properties. Lipofuscin fluorescence is brighter than that of drusen (drusen are common in choroidal nevi).

SD-OCT

Standard spectral domain OCT does not have enough depth imaging for detecting the internal characteristics of choroidal melanomas and other choroidal lesions. But it is useful to visualize changes in the neurosensory retina and the RPE. As it was mentioned earlier, posterior uveal melanomas may show serous retinal detachment in the areas adjacent to the tumor. Lipofuscin deposition is also seen at the level of the RPE.

EDI-OCT

Enhanced Depth Imaging Spectral Domain OCT” is a relatively new technology that is now commercially available. It is a method that allows for the evaluation of deeper structures such as the choroid and the internal portion of the sclera. It is also an alternative to US for measuring tumor thickness. In a study by Carol Shields, et. al. it was found that small choroidal melanomas thickness was overestimated by 55% on US compared with EDI-OCT. Characteristics of choroidal melanomas readily seen in EDI-OCT are:

  • Intraretinal edema.
  • Shaggy photoreceptors.
  • Loss of photoreceptors.
  • Loss of external limiting membrane.
  • Loss of inner segment-outer segment junction.
  • Irregularity of inner plexiform layer.
  • Irregularity of ganglion cell layer.

Laboratory test

Posterior uveal melanomas spread via vortex veins to the blood flow. Most metastasis are to the liver (92%), but the tumor can also invade the lungs and the skin, and can also demonstrate extension into optic nerve and brain. Among the tests included in the metastatic workup in a patient with choroidal melanoma are:

  • Abdominal examination looking for hepatosplenomegaly.
  • Laboratory: Liver function tests.
  • X ray: Chest X ray.


It is recommended, that if any of the above mentioned is abnormal, a chest and abdomen CT/MRI should be carried out.

Differential diagnosis

There is evidence that choroidal melanomas may arise from choroidal nevi, since nevi cells have been found in histopathological samples of melanomas. For this reason, Shields and colleagues analyzed 2,514 cases of choroidal nevi to determine predictive features of growth into melanoma. Using the data obtained in this study, they developed a mnemonic with this predictive features: “To Find Small Ocular Melanoma Using Helpful Hints Daily”. It three or more of this factors are present, they estimated a greater than 50% risk of malignant transformation.

  • T: Thickness > 2 mm.
  • F: Fluid (subretinal).
  • S: Symptoms.
  • O: Orange pigment (presence of).
  • M: Margin within 3 mm of the optic disc.
  • U: Ultrasonographic.
  • H: Hollowness.
  • H: Absence of surrounding halo. Nevi usually show a surrounding clear halo consisting of atrophied retina.
  • D: Absence of drusen. Drusen are chonic changes seen in slow growing lesions such as choroidal nevi.


References

  1. Lewis DA, Albert DM. Chapter 138: Choroidal Nevi. In: Ryan SJ, et. al. Retina. 5th ed. Elsevier, 2013.
  2. Chapter 12: Uveal Tract. In: AAO Basic Clinical and Science Course Section 4: Ophthalmic Pathology and Intraocular Tumors. American Academy of Ophthalmology, San Francisco, 2011-2012.
  3. Cheung A, Scott IU, Murray TG, Shields CL. Distinguishing a Choroidal Nevus from a Choroidal Melanoma. Ophthalmic Pearls, EyeNet Magazine. Feb, 2012.
  4. Chapter 8: Oncology. In: Yannuzzi LA. The Retinal Atlas. Elsevier, 2010.
  5. Chapter 11: Posterior Segment. In: Trattler W, Kaiser PK, Friedman NJ. Review of Ophthalmology. 2nd. Ed. Elsevier. 2012.
  6. Collaborative Ocular Melanoma Study Group. Baseline echographic characteristics of tumors in eyes of patients enrolled in the Collaborative Ocular MelanomaStudy: COMS report no. 29.
  7. Singh P, Sinhg A. Choroidal melanoma. Oman J Ophthalmol. 2012 Jan-Apr; 5(1): 3–9.
  8. Wolff-Korman P, Korman B, Hazeneratz G. Duplex and color Doppler ultra­sound in the differential diagnosis of choroidal tumors. Acta Ophthalmol 1992;204:66–70. Ophthalmology. 2008 Aug;115(8):1390-7, 1397.
  9. Gunduz K, Pulido JS, Bakri SJ, et al. Fundus autofluorescence in choroidal melanocytic lesions. Retina 2007;27:681–7.
  10. Shields CL, Furuta M, Berman EL, et al. Choroidal nevus transformation into melanoma: analysis of 2514 consecutive cases. Arch Ophthalmol 2009;127:981–7.
  11. Shields CL, Kaliki S, Rojanaporn D, Ferenczy SR, Shields JA. Enhanced Depth Imaging Optical Coherence Tomography of Small Choroidal Melanoma. Arch Ophthalmol. 2012 Jul;130(7):850-6.
  12. Torres VL, Brugnoni N, Kaiser PK, et al. Optical coherence tomography enhanced depth imaging of choroidal tumors. Am J Ophthalmol 2011;151:586–93.
  13. Collaborative Ocular Melanoma Study Group. Design and methods of a clinical trial for a rare condition: the Collaborative Ocular Melanoma Study. COMS Report No. 3. Control Clin Trials. 1993 Oct;14(5):362-91.