Late invasive breast cancer after mastectomy for incidentally detected male DCIS: recurrence or new primary?

Ductal carcinoma in situ (DCIS) in men is rare, and its long-term behaviour is not well defined. We report a case of late invasive breast cancer more than two decades after a mastectomy for incidentally detected high-grade DCIS in a 45-year-old man. This case highlights that, although mastectomy for pure DCIS offers excellent local control, invasive occurrence of new primary or local recurrence can still occur. Ongoing awareness and follow-up may therefore be warranted even in male patients treated definitively for DCIS.