In the case of carcinoma breast with Her -2 neu immunohistochemistry staining, which of the following score needs fuher FISH study?

**Core Concept**
Her-2 neu immunohistochemistry staining is used to assess the expression of the human epidermal growth factor receptor 2 (HER2) protein in breast cancer cells. HER2 overexpression is associated with aggressive tumor behavior and poor prognosis. However, immunohistochemistry (IHC) results can be equivocal, necessitating further testing with fluorescence in situ hybridization (FISH) to confirm the presence of HER2 gene amplification.

**Why the Correct Answer is Right**
A FISH study is required when the IHC score is equivocal, meaning that the HER2 protein expression is neither clearly positive nor negative. In the context of breast cancer, a FISH study is typically indicated when the IHC score is 2+ (equivocal). This is because IHC scores can be influenced by various factors, including tissue fixation, staining conditions, and antibody quality. FISH, on the other hand, directly assesses the gene copy number, providing a more accurate diagnosis of HER2 amplification.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incorrect because IHC scores of 0 or 1+ are generally considered negative for HER2 overexpression. Therefore, further FISH study is not typically required for these cases.
**Option B:** This option is likely incorrect because IHC scores of 3+ are generally considered positive for HER2 overexpression. In these cases, FISH study is not typically required to confirm HER2 amplification.
**Option C:** This option is likely incorrect because it is not a valid IHC score for Her-2 neu immunohistochemistry staining.

**Clinical Pearl / High-Yield Fact**
When interpreting Her-2 neu IHC results, it's essential to remember that a score of 2+ indicates equivocal results, which require further FISH study to confirm the presence of HER2 gene amplification. This is a critical distinction, as HER2 overexpression can significantly impact treatment decisions and patient outcomes.

**Correct Answer:** D.