Low power: Pap stain
Cellular sample with predominantly dispersed cells
Medium power: Pap stain
Numerous malignant melanoma cells with enlarged round nuclei, frequent binucleation, prominent nucleoli, occasional intranuclear cytoplasmic inclusion, and moderate amounts of cytoplasm
High power: Pap stain
Malignant melanoma cells in a background of lymphocytes. Note intranuclear cytoplasmic inclusion.
High power: Pap stain
Numerous malignant melanoma cells with enlarged round nuclei, frequent binucleation and moderate amounts of cytoplasm
Medium power: Pap stain
Numerous malignant melanoma cells predominantly singly dispersed. Note binucleation and intranuclear cytoplasmic inclusion, clues to diagnosis.
Features
• Singly dispersed cells
• May be hard to distinguish in a background of mesothelial cells (great mimicker)
• Large cells with increased N:C ratios
• Rarely cytoplasmic melanin pigment
• Enlarged round nuclei
• Nuclei may be eccentrically located
• Frequent binucleation
• Prominent nucleoli
• Intranuclear cytoplasmic inclusions may be seen
• IHC: Tumor cells typically express melanoma markers including S100, HMB45, Sox10, while negative for keratin (D/D carcinoma), calretinin (D/D mesothelial cells) and CD68 or CD163 (histiocytes)