
<b>Immuno-</b>
Immuno-histo-chemical tests use antibodies [that's the immuno part] that will react with a particular cell protein  [like Actin, for instance].  These antibodies have been "tagged" in some way, so that they can be recognized...like with dyes that appear dark under the microscope.   So a thin slice of the wax block containing the tumor is incubated with the antibody-tagged-with-dye, and after a period of time, the tumor slice is washed off and looked at under the microscope.  Where the cell part [like Actin] exists, it will be combined with the antibody carrying the dye.  The dye will show up under the microscope.  Then the tumor is positive for the presence of that protein.  If it doesn't show up, the tumor is negative for the protein.  

<b>-histo-</b>
Tests for Actin, Desmin, and quite a few other cell proteins are what are called immunohistochemical tests. Because many tumors can resemble each other under the microscope, these tests differentiate between LMS, other sarcomas, and other tumors which are not sarcomas but resemble them. These tests tell us that you have LMS and not rhabdomyosarcoma or another type of tumor. They are TUMOR IDENTIFYING tests.  This is histology [looking at the identifying features of cells.]  That is why the -histo- is part of the name of these test.  

<b>-chemical</b>
And it is chemical histology, because it is the identifying of different tissues by different molecules, rather than cell structure and appearance.


<b>Immunohistochemical</b>
Immunohistochemical tests will have been done on your primary tumor, to identify its tissue type, e.g. leiomyosarcoma. We are NOT discussing these kinds of tests further here, but rather discuss tests oriented toward giving treatment choices and/or prognosis.
