Metastatic Breast Cancer in a Patient with Fanconi Anemia

Fanconi anemia (FA) is a rare inherited disorder characterized by progressive bone marrow failure, congenital malformations and a propensity for developing malignancies at an early age. The underlying genetic defect in FA creates a state of cellular hypersensitivity to many traditional chemotherapy agents, making the treatment of malignancies in this population particularly challenging.

We describe a 42-year-old female who presented with a solitary mass in her left breast. Core biopsy revealed an invasive ductal carcinoma that did not express estrogen (ER) or progesterone receptors (PR), but did express human epidermal growth factor receptor 2 (HER2). Staging work-up revealed diffuse skeletal metastatic disease. At her initial consultation with medical oncology, she was discovered to be pancytopenic. Further history revealed a sibling with aplastic anemia and that she had undergone chromosomal breakage testing for FA in the past, which was subsequently confirmed to be positive. She underwent a bone marrow aspirate and biopsy that showed metastatic marrow infiltration by non-hematopoietic cells. In addition there was morphological evidence of dyserythropoiesis and cytogenetic abnormalities on karyotyping, features suggestive of FA. She was initially started on trastuzumab monotherapy. Low dose radiation therapy was added due to local tumor progression. Combined HER2 directed therapy was to be implemented, but was held due to a functional decline in the patient. To date, she has not received definitive genetic testing to determine which FA subgroup she belongs to.

This case highlights two important aspects of FA. The first is the inherent increase in susceptibility to neoplasms in this group, including solid tumors such as breast cancer. The genes associated with FA are involved in deoxyribonucleic acid (DNA) repair pathways, including mutations in the breast cancer susceptibility gene, BRCA2. The second is the heightened sensitivity to the toxic effects of many standard chemotherapy and radiation treatments. This creates unique challenges in the treatment of malignancies in this population and stresses the importance of targeted therapies.