How do you approach a stage IIIC triple positive IDC, s/p neoadjuvant TCH and P, lumpectomy, and ALND with significant residual disease at the time of surgery?  

I would use adjuvant T-DM1 for residual disease after standard neoadjuvant therapy for HER2+ breast cancer as described in this case.  We have strong evidence from the KATHERINE randomized trial that adjuvant T-DM1 compared to trastuzumab that cuts recurrence risk by about 50% in this situation...

My practice would be to switch therapy to T-DM1. Analysis of subgroups in KATHERINE showed benefit whether ER positive or negative, thus there really are no subgroups for which I would consider adjuvant (traditional) cytotoxic chemotherapy, assuming the patient was able to complete neoadjuvant ...

T-DM1 is what I would use.

TDM-1 based on the Katherine trial.

I would agree with T-DM1 based on KATHERINE trial with grain of salt (given clear lack of use with pertuzumab in neoadjuvant settings). However, I would suggest individualizing it. If someone already has DM, G2 or G3 neuropathy, then using T-DM1, risks may outweighs the benefits.