First a request: if you will add any additional posts to your original thread, so that your information will all be in one place, it will help us to provide better answers, as well as help other members who have been following our discussions to know when you have posted again. If possible, please copy and paste your post above onto your original thread:
Now, on to your current questions:
1. A 2 cm mass is fairly large (approaching an inch in diameter), At 2cm, it is on the upper limit of the T1 category in the TNM classifcation system for determining the Stage of a person's BC. Above 2cm it would be a T2. (This probably doesn't mean too much to you, but as your doctor indicated, it is used in tx planning.)
2. As tamos indicated above, ER and PR are parts of your "hormone receptor status" and ER+/PR+ is considered favorable, because there are targeted treatments (tamoxifen and AIs) for it which can significantly reduce your risk for recurrence.
3. The fact that you have no lymph node involvement (meaning cancer cells appear not to have spread from your tumor to the axillary lymph nodes) is another good-news finding.
4. HER2+ staus is a concern, because this indicates an aggressive type of BC with an increased risk of recurrence. For this reason, the latest view is that even small HER2+ tumors call for tx with both chemo and Herceptin (a targeted tx for HER2+ BC).
"From the San Antonio Breast Conference in December, new data shows a higher than predicted rate of breast cancer recurrence even with very small breast cancers that are HER2 positive. The data is from the first large study to analyze early-stage breast cancer patients with HER2 positive tumors one centimeter or smaller. All these women would benefit from adjuvant Trastuzumab, also known as Herceptin, (for one year, the standard in America) - along with adjuvant chemotherapy. This represents a shift in the way women with early-stage HER2 positive breast cancer should be assessed for risk of recurrence and considered for treatment, according to the study's author."
4. All of this does not mean you made the "wrong choice" in having a lumpectomy, because in cases where either approach was an option, studies have not found a difference in survival rate related to which surgery was chosen by the patient. However, many women are still choosing mastectomies even when they are not considered medically necessary. These are the most common reasons given for that choice:
1. If no spread to nodes, then didn't need to go through radiation if took mast. route. 2. Wanted to make sure it was completely gone. 3. Esp. with older women, some were more concerned about survival and the strain and inconvenience of returning repeatedly for radiation (esp. where access to care and poverty were issues), than with appearance. 4. Even with younger women, if a person's breasts are on the small side, a lumpectomy for a larger growth may not leave a cosmetically pleasing result, making mast. and reconstructive surgery preferable.
A mastectomy is still an option if that is what you want, but the best timing for it is something you would best discuss with your treatment team.