FISH (fluorescence in situ hybridization) is a technique used to identify specific and predefined genetic genetic changes in myeloma (and in other cancers as well). Typically, FISH results are based on the staining of 200 (in some cases 100) myeloma cells. A positive result is based in the percent of cells above a "baseline" lower limit or threshold depending on the test facility.
Your father was initially positive for del17p (TP53) and then with therapy that component or subclone (a topic in of itself) of myeloma cells has now dropped below the limits of detection. The unfortunate reality is that although it is not detected, it is still there- just too low to detect. For example, before it was 40/200 myeloma cells examined (20%)- now it might be 1/200 or less cells (0.5%)- below what is "positive for the test.". He has not changed to standard risk.
I generally count on the percentage of plasma cells from the core biopsy as a marker of bone marrow involvement. The flow cytometry - based on the aspirate frequently under represents the myeloma bone marrow burden for a couple of reasons 1) myeloma cells are closely adherent to the matrix and there for do not all get released into the aspirate (liquid part of marrow) and 2) myeloma cells tend to shed CD138 when stressed.
For your father - those numbers are essentially identical. And taking an average is just fine. But I would try to compare the core percentages (CD138+).
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Re: Can FISH be wrong?
Thanks, Dr. Shain.
For the FISH, the biopsy was done on a "2.1cm core."
Sorry, I have another question. At the bottom there's a remarks that say: "flow cytrometry of bone marrow demonstrate ~0.1% atypical plasma cells which express CD138+, CD38+, CD56- and CD19-, with cytoplasmic kappa light chain restriction." What does that ~0.1% represent?
Also, just a side info, my Doc said something weird about the results. He said: "it did not show 17p deletion. Don’t know how to explain that. It showed t11,14 on histology , although FISH was not showing a translocation. Both the tests should be positive or negative simultaneously and I cannot explain this disparity." Probably it is good to let you know that this is my 2nd Doc. The 1st Doc, who diagnosed Dad, told me right on my face that he does not know much about highrisk multiple myeloma.
Thanks much for your help.
For the FISH, the biopsy was done on a "2.1cm core."
Sorry, I have another question. At the bottom there's a remarks that say: "flow cytrometry of bone marrow demonstrate ~0.1% atypical plasma cells which express CD138+, CD38+, CD56- and CD19-, with cytoplasmic kappa light chain restriction." What does that ~0.1% represent?
Also, just a side info, my Doc said something weird about the results. He said: "it did not show 17p deletion. Don’t know how to explain that. It showed t11,14 on histology , although FISH was not showing a translocation. Both the tests should be positive or negative simultaneously and I cannot explain this disparity." Probably it is good to let you know that this is my 2nd Doc. The 1st Doc, who diagnosed Dad, told me right on my face that he does not know much about highrisk multiple myeloma.
Thanks much for your help.
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