When investigating the effects of LSD1 on MCC growth, we noticed that MCC cells in vivo changed from relatively uniform, small, round to oval cells with round nuclei and scant cytoplasm in vehicle‐treated mice to slightly larger and elongated cells with irregular‐shaped nuclei and ill‐defined cell borders in LSD1‐treated tumors (Fig 3M). Here, KDM1A is linked to Merkel cell skin cancer.