Ennen and coworkers performed an analysis of the MITF-high and MITF-low transcriptional profiles at the level of single melanoma tumor cells isolated from various lesions of five different melanoma patients, and reached two important conclusions: single-cell expression analysis revealed inter- and intra-tumor heterogeneity in primary melanoma; importantly and interestingly, primary melanomas comprise subpopulations of tumor cells co-expressing genes of the MITF-high and MITF-low signatures at the level of single cells [184]. The gene discussed is MITF; the disease is melanoma.