ESR1 and breast cancer: Current research on the neurobiological mechanisms underlying these breast cancer behavioral comorbidities has limitations as many rodent models are lacking critical components of the typical breast cancer paradigm: syngeneic, orthotopic, estrogen receptor positive (ER+) tumors (often no tumors), post-menopausal reproductive status (many studies in males), tumor resection surgery, repeated chemotherapy cycles, and various other consecutive treatments (e.g., aromatase inhibitors).