What happened, in summary

A 67-year-old woman with chronic lung disease developed 3 weeks of increasing redness, rash, swelling, itching and pain in her right breast. Antibiotics for suspected mastitis did not improve the symptoms. She had previously been diagnosed in May 2008 with Stage III adenocarcinoma of the right lung that was EGFR positive. Her lung-cancer treatment had included mediastinal radiation with weekly paclitaxel and carboplatin over 6 months, followed by erlotinib. Erlotinib was later restarted intermittently for suspected recurrence but was ultimately stopped in July 2014 because of severe skin toxicity. The new breast changes resembled inflammatory breast cancer, but biopsy showed moderately differentiated adenocarcinoma consistent with her lung primary rather than a new breast cancer. The metastatic cells were TTF-1, napsin and CK7 positive and negative for breast-associated markers GATA-3 and GCDFP-15. This established the breast as a distant metastatic site from the lung cancer. She chose radiation and completed 15 fractions to the breast. A subsequent PET scan showed no metabolically active cancer. She died 2 months after the breast metastasis was diagnosed.