Using tumor expression data and non-negative matrix factorization, Gay et al. identified four SCLC subtypes defined largely by differential expression of transcription factors ASCL1, NEUROD1, and POU2F3 or low expression of all three transcription factor signatures accompanied by an Inflamed gene signature (SCLC-A, N, P, and I, respectively). Here, ASCL1 is linked to small cell lung carcinoma.