PTEN and PIK3CA Mutation Positive Breast Neuroendocrine Carcinoma Treated with Molecularly Targeted Therapy Including Capivasertib

Breast neuroendocrine carcinoma (BNEC) is rare (<0.1%) but is clinically important due to its rapidly progression, treatment-resistant, and poor prognosis despite being hormone receptors-positive.No effective treatment for BNEC has been established.BNEC is little recognized, so it may be overlooked as an invasive carcinoma of no special type.However, an early diagnosis of BNEC is critical, as it allows for comprehensive genomic profiling (CGP).We present a case of a woman in her 40s with heterochronic bilateral breast cancer, who was ultimately diagnosed with BNEC due to the rapid disease progression with bone, liver, and lung metastases, during semiannual follow-up.CGP revealed PTEN, PIK3CA, and ESR1 mutations as well as a high tumor mutational burden (TMB-high).While she received everolimus, abemaciclib, and bevacizumab, capivasertib was most effective.BNEC is rare, but an early diagnosis, based on clinical course, is key for CGP and correct treatment selection.