Pathology of the Head and Neck

Eye and Ocular Adnexa Chapter 10 299Fig. 10.19. Uveal tract melanoma arising in the choroidFig. 10.20. Uveal tract melanoma: detail of closely packed spindle-shapedcells; in this area almost no pigment is presentIn the ciliary body naevi are very rare; the histologyis comparable with iris naevi: spindle-shaped cellswithout atypia and without mitotic figures. In the choroid,naevus cells are spindle-shaped and often heavilypigmented, nuclei are uniform, and no mitotic figuresare seen. Depigmentation of the slides may be helpful inevaluating cytological details.10.4.5.1.2 Malignant MelanomaICD-O:8720/3The major part of uveal tract melanomas arise in thechoroid (Fig. 10.19). Most frequently affected are whiteindividuals in the sixth and seventh decades of life.Most melanomas are single and confined to one eye.In most cases they arise from pre-existing naevi in thechoroid. Ciliary body and iris melanomas are rare.Malignant melanoma of the choroid presents with lossof vision in one eye, or with secondary closed angleglaucoma. The glaucoma is caused by detachment ofthe retina with lens–pupil block. Spread of the tumourinto the orbita can cause proptosis. The primary clinicaldifferential diagnosis for melanoma is choroidalmetastasis. At macroscopic examination of an enucleatedeye with a choroidal melanoma, it is important tolocate the tumour before cutting the eye. The tumourcan be located by palpation and transillumination. Ifpossible, the main histological section should containthe centre of the pupil, the optic nerve and the centreof the tumour. Small pigmented nodules can be seenon the external surface of the sclera in case of transscleralextension of the tumour. The sample taken atthis point sometimes needs section at multiple levelsto demonstrate the tumour passing through the scleralcanals. Microscopically, the melanomas consist ofFig. 10.21. Uveal tract melanoma: a more pigmented areaspindle-shaped cells, epithelioid cells, or a combinationof both (mixed cell type). The spindle-shapedcells are closely packed elongated cells, often with pronouncednucleoli and a few mitotic figures. In epithelioidlesions, the cytoplasm is more eosinophilic andmitotic figures are easily found. Melanin pigment isusually is present, but amelanotic lesions can be seen(Figs. 10.20–10.23). Positive immunohistochemistrywith S-100, melan A or HMB45 confirms the diagnosisin those cases. The final report should include theorigin of the tumour (choroid, ciliary body, iris), thethickness of the tumour (in mm), the cell type (spindlecell type, epithelioid cell type or mixed cell type) andextraocular growth. The 5-year survival of pure spindletumours is 80%, while pure epithelioid tumourshave a 5-year survival of 35%. The 20-year survival ofboth groups is only 20%.