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p53 and tumor block was posted 05/20/2001 05:20 pm by peter argani
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Hi Elizabeth: As usual, you are asking very good questions. I will try to answer them in order. 1. It is not uncommon for bile duct tumors to be small and have a low percentage of tumor cells within them. They tend to be small when they are located distally and block the bile duct early; this results in symptoms of jaundice which brings people to the doctor. The prognosis is generally better when the tumor is smaller. Like pancreas cancer, bile duct carcinomas are almost always associated with a large reactive scar around them (also known as desmoplastic reaction). The scar tissue itself is benign, and it is a reaction to the bile duct cancer cells. Therefore, in a bile duct tumor mass, the majority of the cells that make up the mass may be benign fibroblasts that make up the benign scar. There still are cancer cells in the mass; they just are outnumbered. 2 and 3. The immunohistochemical stain for p53 tells us how many of the tumor cells express detectable p53 protein. The noncancer cells are not included in this result. In general, p53 is not detectable by immunohistochemistry in normal bile duct epithelium or any other normal tissue. p53 protein expression by immunohistochemistry is an imperfect but still valuable test that correlates with p53 gene mutation. Usually, mutated p53 protein persists longer in the cell than normal p53, and hence it becomes detected by immunohistochemistry. Tumors in which a high percentage of the tumor cells overexpress p53 protein (>30%) are very likely to have p53 mutations in them, while those that express little p53 protein (<10% of cells) are unlikely to have p53 mutations. It is hard to predict if p53 is mutated in tumors that are express p53 in 10-30% of cells.

I hope this is helpful. take care peter

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