Mary is a $60-$year$-$old woman who was diagnosed with Stage II breast cancer after her routine mammogram identified masses at the $9$ p$.$m$.$ position in her right breast. Mary underwent a needle biopsy, and it was determined that there is an invasive ductal carcinoma $($IDC$)$ that is estrogen and progesterone receptor positive. As with most breast cancer diagnoses surgical treatment is primary treatment. Mary underwent a modified radical mastectomy with lymph node dissection. It was noted that the sentinel lymph node and $9$ of the $16$ lymph nodes were identified as positive for tumor cells. The tumor identified is $2\mathrm{.}1$cm x $4\mathrm{.}7$cm$.$ 

$1.$ What is the significance of identifying a positive sentinel node during the surgery? $(1$ mark$)$ How and when would this be identified? $(2$ marks$)$

$2.$ What is the purpose and importance of treatment by identifying the hormone$-$receptor status of this cancer? $(2$ marks$)$

$3.$ Describe the modified radical mastectomy that Mary underwent. $(3$ marks$)$