Complex sentence: Uveal Melanoma is cancer (melanoma) of the eye involving the iris, ciliary body, or choroid (collectively referred to as the uvea) with advanced tumors encompassing more than one of these structures.
Split into simpler sentences: Uveal Melanoma is cancer (melanoma) of the colored part of the eye and the surrounding areas (uvea). Tumors arise from the iris, ciliary body, or choroid at the back of the eye, and advanced tumors can encompass more than one of these structures.