Indeed, it is well known that 18F-FDG uptake in BC depends on many factors such as tumor grading (low-grading lesions showing lower uptake), histologic types (lobular carcinomas showing lower uptake than invasive ductal carcinomas), hormonal receptor status (lower uptake in estrogen-positive and progesterone-positive well-differentiated tumors than hormonal receptor-negative tumors) and molecular subtypes (Luminal A showing lower uptake than others, due to a generally low-grading and low mitotic activity) [53,54]. The gene discussed is NR4A1; the disease is breast cancer.