YAP1 and small cell lung carcinoma: Additionally, it is important to note that the subtype-defining potential of YAP1 has recently been fundamentally questioned as multiomic reassessment of the presumed YAP1-high SCLC cell lines (that served as the basis for the original classification scheme) revealed that nearly all of these tumors are actually previously unrecognized SMARCA4-deficient undifferentiated tumors or other types of malignancies rather than SCLC.51