Histologic Features

In these tumors, cells develop cytoplasmic vacuoles that resemble signet ring cells seen in mucin-producing adenocarcinomas (lower arrow). These vacuoles do not stain for mucin. Sometimes the vacuoles contain RBCs (upper arrow) that indicate formation of vessels. These cells, as well as tumor cells without evidence of vessel formation, stain for endothelial cell products. What are these stains? Answer

Note that compared to those at the periphery, these tumor cells are smaller, have more irregular shapes, and have ill-defined cytoplasmic boundaries .

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Answer: Immunoperoxidase stains for factor VIII-related antigen, CD 31, and CD 34, and reaction with the lectin Ulex europeus-1.

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