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Breast imaging – Mammography interpretation – Understanding the normal mammogram – Physiological variations


Breasts can have physiological changes, and it is important to be able to recognize these when evaluating the normal mammogram. The normal variants commonly seen are the following:
  • Polymastia
  • Inverted nipple
  • Asymmetrical breast tissue.

Polymastia (accessory breasts)
An accessory breast is the presence of breast tissue in addition to the normal breasts. The accessory breast may be present anywhere along the embryological mammary line (from the anterior axillary fold to the inguinal region).

Inverted nipple
A mammography finding of inverted nipple is characterized by nipple inversion in the absence of an underlying retroareolar or parenchymal lesion. The breast parenchyma does not reveal a suspicious mass or microcalcifications. There is no evidence of surgical intervention or trauma. The diagnosis of physiological inverted nipple is then confirmed. It is of three grades:
  • Grade 1: Nipple can be pulled out manually and will retain its projection.
  • Grade 2: Nipple can be pulled out manually, but will retract after release of pressure.
  • Grade 3: Nipple cannot be pulled out manually and is severely inverted and retracted.
Click on the following links to view examples of cases: grade 1, grade 2, and grade 3.

Grade 1 inverted nipple

Grade 2 inverted nipple

Grade 3 inverted nipple

Asymmetrical breast tissue When an area of one breast has a different volume from the same area of the other breast, it is called asymmetry. Asymmetrical breast tissue is usually normal and caused by hormonal changes during puberty that vary in both breasts. An absence of mass and microcalcifications within the asymmetry confirms that it is a normal variant. An asymmetrical volume of fibroglandular parenchyma with no features of architectural distortion or underlying mass is a common finding on mammography.

Some other normal variants
  • Breast hypoplasia is underdevelopment of the breast. It may be congenital or acquired.
  • Amastia is the absence of breast tissue, nipple, and areola. It is a rare congenital condition and may be unilateral or bilateral.
  • Amazia is the absence of glandular parenchyma in either one or both of the breasts with a normal nipple–areolar complex.
  • Polythelia (supernumerary nipple) is the presence of accessory nipples.


Click on the pictures to magnify and display the legends

Click on this icon to display a case study

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