CD274 and epithelioid cell melanoma: PDL1-positive cells were observed in the eye section of an 8-week-old human embryo in the retina and choroids, retinoblastomas (retina, choroids, and tumor tissue) (Figure 4b), and various types of melanomas (retina, choroids, and tumor tissue) (Figure 4d), with the exception of epithelioid melanoma, which had no PDL1 expression in the choroids.