More detailed analysis accumulating over the last years suggests that MCC cells (CK20+, CD56+, CKAE1/AE3+, NSE+, PAX5+, NSP+, TdT+, SATB2+, TTF-1−, LCA−, S100−, p40−, chromogranin+/−, and synaptophysin+/−) are not the progeny of mature Merkel cells (Cytokeratin 20—CK20+), and the true origin of MCC remains unknown [1]. The gene discussed is TTF1; the disease is Merkel cell skin cancer.