FIGURE 4.

A–C: Melanoma cells from primary uveal melanoma tissue. A: Spindle A cells, featuring a longitudinal fold through the long axis of the nuclei and inconspicuous nucleoli. B: Spindle B cells, featuring a more open nucleus than seen in spindle A cells and prominent nucleoli. C: Epithelioid cells, featuring round cytoplasm, large nuclei, and exceptionally large pleomorphic nucleoli. D: DIC micrograph of a dot culture. Epithelioid MUM2B melanoma cells were seeded dots of Matrigel arranged in a grid on a glass coverslip. At day 5, MUM2B cells in contact with the edge of the dot of Matrigel (asterisk) began to form vasculogenic mimicry patterns. Note the elongated shape and the longitudinal fold through the long axis of the nucleus (white arrow). In contrast to MUM2B cells on plastic that feature a round nucleus with prominent nucleoli, the nucleolus of the spindled MUM2B melanoma cells is barely detectable by DIC microscopy. E: Same field as in D after staining for fibrillarin and DAPI counterstaining. The nucleoli of the spindled MUM2B cells on the edge of the Matrigel dot are extremely small (white arrow) compared with epithelioid cells on the coverslip. Epithelioid cells on the Matrigel dot (to the right of the spindled cell denoted by the arrow) formed vasculogenic mimicry patterns between days 5 and 10 and also assumed a spindled morphology. A–C: H&E. Scale bars = 10 μm. D: DIC microscopy captured through laser-scanning confocal microscope. E: Laser scanning confocal microscopy, section plane thickness = 2 μm.