What treatment would you recommend for DCIS incidentally found in pathologic specimen following breast reduction surgery?

This is a challenging situation that can be seen in spite of evaluation prior to definitive procedure. I would agree with an MRI after the patient heals to look for any obvious residual disease.

In the absence of a completion mastectomy which is usually unlikely, I would favor a course of whole breast radiation. Pathologic specimen typically cannot be localized and is not oriented so I would not favor any partial breast approach.

Additionally, boost is challenging as the tumor location is unknown.

Continue to follow the patient very closely.

Based on the age and high risk pathology, would favor RT.

That being said, would do breast MRI once healed to rule out any gross residual disease missed on mammogram.

These are challenging situations and often margin status cannot be determined. We counsel the patient that the only way to truly know all DCIS has been removed is with mastectomy though this is a substantial operation. The patient can also consider whole breast RT but we usually can't boost given the inability to localize where DCIS was and if there is truly a positive margin, this could lead to inferior local control and outcomes.

There are multiple studies showing low local failure rates following whole-breast irradiation without breast surgery for patients presenting with axillary adenopathy with no apparent primary lesion in the breast on mammograms or MRI (e.g., Rueth et al., PMID 25249256). However, we do know if this patient's situation is really analogous. The residual tumor burden in the current patient may be considerably larger than in patients in the "axillary presentation" series. (It was not stated whether this patient had preoperative imaging or not.) The latter patients also generally receive intense systemic therapy and are older than this patient. Hence, my own philosophy in patients such as this one is to NOT irradiate at present. Should surveillanc...