Multiple receptor conversions during the course of metastatic breast cancer therapy: a case report and review of the literature.

backgroundAdjuvant systemic therapy decreases recurrence and death from breast cancer, but late relapse still occurs. Therapeutic decisions are based heavily on receptor tissue characterization. Even though the vast majority of metastatic sites do not have receptor conversions, they can occur at the time of metastasis and/or during the course of treatment. However, multiple receptor conversions are uncommon. CASE PRESENTATION: We present an unusual case of a Caucasian patient originally diagnosed with an estrogen receptor-positive, progesterone receptor-positive, and human epidermal growth factor receptor 2-negative primary breast cancer who had a recurrence after 15 years of therapy. Her metastatic tumor had a different receptor status than the original tumor. During the course of therapy, at the time of progression, a new biopsy showed that her tumor had changed once more. CONCLUSION/DISCUSSION: Tracking receptor conversions is important in metastatic breast cancer treatment. Single receptor conversions have been documented to occur, but not much is known of multiple receptor conversions. This case sheds light on the possibility of patients having multiple receptor conversions and the importance of performing multiple biopsies during the course of metastatic treatment.