MSX1-positive cells were observed in the eye section of an 8-week-old human embryo in the retina and choroid (Figure 4a), in retinoblastoma (retina, choroid, and tumor tissue) (Figure 4b), in spindle melanoma (retina, choroid, and tumor tissue), in myxoid only in tumor tissue (Figure 4d), and in epithelioid melanoma in the retina and choroid. Here, MSX1 is linked to retinoblastoma.