When considering patients with oncological diseases, prognostic indicators such as mitotic indices (e.g., argyrophilic nucleolar organizer regions, Ki-67, and proliferating cell nuclear antigen) [61], nucleotide polymorphisms in HER-2/neu, BRCA1, and P53 genes [62], and levels of E-cadherin expression [63] as markers of tumor grade and metastatic process in mast cell tumors, mammary cancer, and squamous cell carcinomas should be taken into account. The gene discussed is ERBB2; the disease is breast cancer.