2.4. Mammary gland whole‐mount staining

Mammary gland whole‐mount staining was performed following standard procedures [²³]. Briefly, mammary glands were fixed on glass slides with Carnoy's solution (glacial acetic acid: chloroform: ethanol, 1:3:6) overnight at room temperature (RT). The glands were rehydrated prior to overnight staining in aluminum carmine; for that staining, carmine (1 g) and aluminum potassium sulfate (2.5 g) were boiled for 20 min in distilled water, filtered and brought to a final volume of 500 mL. The glands were then stored in 70% ethanol at 4°C overnight. Photographs were taken under an objective lens (4 × magnification) using a digital camera mounted on a Leica MZ12.5 microscope (Leica Instruments, Wetzlar, Germany). The tumor area was quantified using Image‐Pro Plus software (Media Cybernetics, Rockville, MD, USA).