Metaplastic carcinoma (MC) of the breast is usually associated with the triple negative subtype. Recent studies of gene expression have demonstrated the existence of several “molecular” subtypes among the TNBC. According to Lehman and al., six molecular subtypes were identified. These subtypes might have different sensitivity to treatments and different prognosis. Data are very limited and few systemic treatment options are available. Overall the prognosis is usually poor.
We report the case of a 31-year-old woman with de novo metastatic MC to the liver. The histology is in favor of a mesenchymal and sarcomatoid differentiation. The patient was diagnosed during the last two months of her first pregnancy. Soon after the delivery, she was treated with standard weekly Carboplatin-Paclitaxel in combination with atezolizumab (anti-PDL-1) every 3 weeks. PDL-1 was expressed in the tumor and we note the presence for about five percent of Tumor Infiltrating Lymphocytes (TIL). She experienced a complete metabolic response after eight cycles of therapy.
However, soon after the end of chemotherapy and under atezolizumab “maintenance”, the disease progressed with an extension to other sites (bones, nodes, pulmonary). We initiated an anthracyclin-based chemotherapy without tumor response. Currently, she is treated with cyclophosphamide, metothrexate, 5FU, vincristine and prednisone (CMF-VP).
Targeted DNA sequencing performed on a liver biopsy revealed no BRCA mutation but a PI3K-CA mutation (protein H1047R) who is the one of three most frequent pathogenic mutation, causing increased enzymatic kinase activity and increased downstream signalling. A PI3K-CA inhibitor could be a therapeutic option in this patient.
The routine clinical use of molecular TNBC subtypes is not yet validated, however, the use of those categories for the selection of patients for clinical trials is highly recommended.
This case is highly illustrative of the need for a personalized medicine approach in rare breast cancer subtypes which usually types poorly responsive to chemotherapy.