Why did my breast cancer come back as HER2-positive after being triple negative?

Hello and Blessings to all my pink sisters, I had my oncologist consult on October 23 2025, I had my port removed in May of 2025 after having not used if for over 11 months and was starting to have numbness in arm and fingers it had to come out and i thought i was ok .I had two mammogram after my chemo treatment and then lumpetocomy with clean margins was going to do radiation therapy but got knocked down with Adrenal Insufficiency in hospital for 7 Days and had to have physical therapy to gain strength in my legs again, but anyway i will do Radiation this time has anyone up here been diagnosed with a different type of cancer after first one was taken out it was triple negative first time in 2022 with all clean margins now in 2025they say its HERS- positive recently diagnosed in October and since i can't get chemo right now because my viens are so very small they have to use vein finder to find vein anything i am getting any type of IV Fluids Or like having my last surgery that had to use vein finder to even start IV.I have already had surgery on October 7 2025 thanks to my awesome surgeon it 1.4 mm and she said Margins were all clean but i will do radiation this time and will be getting injection in leg of Herceptin or trastuzumab every three weeks. Has any of my pink sisters or anyone with cancer used this medication before .I do have CKD ,only one kidney ,adrenal insufficiency and neuropathy in my feet another reason I am not getting chemo right now until i am able to have another port if i need it later.