This closely resembles the well-studied behavior of commonly encountered small cell lung carcinomas which are rapidly proliferating and have an initially favorable response, but nearly universally relapse.7 Unlike the other PBNENs which tend to express ER and PR, the SCNCB subtype tends to have low hormone receptor expression and can fall into the larger category of TNBC.8 Thus, the “triple negative” nature of SCNCB and its aggressive nature lends its treatment to be similar to that of TNBC. The gene discussed is ESR1; the disease is small cell lung carcinoma.