According to several long-term follow-up studies, the Ki-67 marker could be used to classify some cancer patients, including those with breast cancer.13,36 In addition, several studies have shown an association between Ki-67 expression and the thickness of cutaneous melanoma lesions, as well as a relationship between Ki-67 expression and the tumor’s long-term prognosis.19 However, the effect of this marker on the long-term prognosis of mucosal melanoma requires further studies. The gene discussed is MKI67; the disease is breast cancer.