Breast fat !

Breast fat is the fatty tissue that gives the breast most of its volume; a fattier breast makes a lump easier to see on a mammogram.

Official name: Body of breast

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What it is

The fat that fills the breast around and between the lobes; it gives the breast most of its size and shape.

What it does

Shapes and cushions the breast. With age, and after menopause, fat replaces much of the gland.

Key facts

Where: Subcutaneous and interlobar adipose tissue surrounding the glandular lobes (absent under the areola)
Function: Gives most of the breast volume and shape; proportion to gland sets mammographic density

Relations

Superficial: Skin and the subcutaneous fat layer, in the superficial layer of the superficial fascia
Deep: Retromammary space and the pectoral fascia over the pectoralis major
Contents: The suspensory ligaments of the breast (Cooper) cross it, with the vessels, nerves and lymphatics on their way to the lobes

On imaging

Mammography: fat is radiolucent (dark). Ultrasound: fat lobules are grey and darker than the bright fibroglandular tissue. MRI uses fat-suppressed sequences so that enhancing lesions stand out; fat necrosis may show as an oil cyst with eggshell calcification on mammography.

Common problems

Breast density: breasts with more gland and less fat (dense breasts) make mammograms harder to read and carry a somewhat higher risk of cancer.
Fat necrosis after an injury or surgery: a firm lump that can look like cancer.

How it is diagnosed

The mammography report states the density (from almost all fat to extremely dense); ultrasound or MRI may be added for dense breasts.

Treatment

Fat necrosis: usually no treatment once a biopsy has ruled out cancer.

Clinical notes

Fat necrosis follows trauma, surgery or radiotherapy and can feel hard and fixed, imitating cancer; imaging or biopsy separates them
Lipoma is a soft, mobile, benign fatty lump; on imaging it matches the surrounding fat
Fat grafting from another part of the body is used to reshape the breast after reconstruction or to fill contour defects

Development

Breast budding is usually the first visible sign of puberty. Under oestrogen the ducts lengthen and branch, but most of the growth in size comes from fat laid down around the lobes, which is why breast size says little about milk production.

Test yourself

Think of the answer, then tap the question to see it.

Why can a dense breast hide a tumour on mammography while a fatty breast makes it stand out?

Breast fat is dark on mammography, while gland is white like most tumours; the less fat, the harder a mass is to see.

What are the BI-RADS breast density grades?

a, almost entirely fatty; b, scattered fibroglandular tissue; c, heterogeneously dense; d, extremely dense.

What is fat necrosis of the breast, and why does it matter?

Damage to breast fat after trauma, surgery or radiotherapy; it can feel hard and fixed, imitating cancer, so imaging or biopsy separates them.

Why does obesity raise the risk of postmenopausal breast cancer?

After menopause, adipose tissue is a main site of oestrogen production.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): corpus mammae TA2 7098
Official Spanish (DeCS): Cuerpo de la mama (tejido adiposo)
English (TA2): Body of breast

Sources: Terminologia Anatomica (TA2); Anatomy, Thorax, Breast; Anatomy, Thorax: Mammary Gland; 27.2 Anatomy and Physiology of the Ovarian Reproductive System (OpenStax (Rice University), 2022) · adapted, CC BY 4.0; 27.3 Development of the Male and Female Reproductive Systems (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.

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Representative model, for educational purposes only.