Uveal melanoma classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Uveal melanoma may be classified into several subtypes based on their location, based on ophthalmoscopic examination and based on the cell type. According to the Callender classification, there are four subtypes of uveal melanoma based on the cell type.
Classification
Classification based on location
- Posterior uveal melanoma
- Posterior uveal melanoma refers to the involvement of the posterior choroid. The choroid posterior to the equator, is referred to as the posterior choroid, and is the most common site involved in uveal melanoma. Approximately 85% of cases of uveal melanoma are localized to this region.
- Anterior uveal melanoma
- Anterior uveal melanoma refers to the involvement of the iris, ciliary body, and/or choroid anterior to the equator. Anterior uveal melanoma comprises approximately 9-15% of uveal melanomas.
Classification based on ophthalmoscopic examination
Kanski and Eichhorn-Mulligan et all classified choroidal pigmented lesions into three groups based on ophthalmoscopic examination.[1][2]
- Group I
- The first group is benign and is characterized by small, flat, unchanging lesions that clearly appear as choroidal nevi on ophthalmoscopic exam without observation of the features that suggest metastasis such as macular involvement, large-caliber vessels, serous retinal detachment, and lesion thickness greater than 2.5 mm.
- Group II
- The second group is described as intermediate lesions.
- These lesions are small with thickness less than 2.5 mm.
- These lesions may have subretinal fluid or an orange lipofuscin pigmentation and one of the features suggestive of melanoma mentioned above. The second group is described as intermediate lesions; these lesions are small with thickness less than 2.5 mm that may have an orange lipofuscin pigmentation or subretinal fluid and one of the features suggestive of melanoma such as macular involvement, large-caliber vessels, and serous retinal detachment.
- Group III
- The third group has the highest risk of melanoma.
- These lesions are often large, dome or mushroom shaped choroidal tumors with surface vasculature and orange lipofuscin pigmentation.
- The tumor thickness is greater than 2.5 mm.
Classification based on size
According to Collaborative Ocular Melanoma Study Group, there are three types of uveal melanoma based on tumor size.[3]
- Small melanomas are 1.0 - 2.5 mm in apical height and > 5.0 mm in largest basal dimension.
- Medium tumors are defined as tumors 2.5 to 10 mm in apical height and ≤ 16 mm in largest basal diameter.
- Large tumors are ≥ 2 mm in apical height and > 16 mm in maximal basal diameter, or a melanoma > 10 mm in apical height, regardless of the basal diameter.
Classification based on cell type
Uveal melanomas originate from melanocytes in the uveal tract. According to the revised Callender classification there are four distinct cellular types:[4]
- Spindle-A cells (spindle-shaped cells with slender nuclei and lacking visible nucleoli)
- Spindle-B cells (spindle-shaped cells with larger nuclei and distinct nucleoli)
- Epithelioid cells (larger polygonal cells with one or more prominent nucleoli)
- Intermediate cells (similar to but smaller than epithelioid cells)
Most primary intraocular melanomas contain variable proportions of epithelioid, spindle-A, and spindle-B cells (mixed-cell melanomas). Pure epithelioid-cell primary melanomas are infrequent (approximately 3% of cases). In the Collaborative Ocular Melanoma Study, mixed-cell type melanomas predominated (86% of cases).
References
- ↑ Shields, C. L (2001). "Factors associated with elevated intraocular pressure in eyes with iris melanoma". British Journal of Ophthalmology. 85 (6): 666–669. doi:10.1136/bjo.85.6.666. ISSN 0007-1161.
- ↑ Kanski, Jack J. Clinical diagnosis in ophthalmology. St. Louis, Mo. London: Elsevier Mosby, 2006. Print.
- ↑ van, J.G.M.; Koopmans, A.E.; Verdijk, R.M.; Naus, N.C.; de, A.; Kilic, E. (2013). "Diagnosis, Histopathologic and Genetic Classification of Uveal Melanoma". doi:10.5772/53631.
- ↑ Uveal melanoma. National Cancer Institute(2015) http://www.cancer.gov/types/eye/hp/intraocular-melanoma-treatment-pdq#section/_95 Accessed on October 20 2015