Fine-needle aspiration biopsy (FNAB) of choroidal tumor. A, Cytologic liquid-based preparation displays prominent nucleoli (arrow) and some brown pigment (arrowhead) suggestive of melanoma. B, Cell block of the aspirated cells, stained with HMB-45 using a red chromogen, is positive, confirming the diagnosis of melanoma. Notice the difference between the red chromogen (arrows) and the brown melanin (arrowheads).