This test is aimed at identifying HER2 positive status of the breast cancer cells. SPoT-Light HER2 CISH, stands for Subtraction Probe Technology Chromogenic In Situ Hybridization. In HER2-positive cells numerous HER2 receptor proteins are present at the breast cancer cell surface. From outside these receptors receive signals for the cancer cells to multiply, grow and divide aggressively.
It identifies the HER2 status of the breast cancer cells by detecting HER2 genes in the tissue sample. In this test a stain is used which highlights the HER2 genes. After staining the sample is examined under microscope which shows the number of HER2 genes which have changed colour by absorbing the stain molecules. The pathologist can identify the number of genes copies in the sample. High number of copies of HER2 genes means extra receptor proteins at the cell surface. This test cannot be done of frozen tissue sample, it gives best results in fresh or wax preserved or chemical treated samples. A score of positive and negative is given to measure the HER2 status of the breast cancer cell tissue sample.
It has been observed that in the same cancer growth different parts of the growth may test positive and some may test negative for HER2 receptors. These results may be diagnosed as HER 2 positive for an HER2 negative score in some cases. This is because different lbs and different pathologist have different scoring system for receptor strength. A wrong diagnosis may lead to a faulted treatment which may not benefit the women diagnosed. This is due to the fact that different lbs and different pathologists have different scoring criteria. Also if one part tests as negative and one part of breast cancer is HER 2 positive the doctor may not recommend medicines that would work against HER2 positive growth.