Retromammary space !

The retromammary space is a thin layer of loose tissue behind the breast that lets it glide over the chest muscle; a cancer fixed to the muscle is advanced.

Official name: Pectoral fascia

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What it is

A thin layer of loose fat between the back of the breast and the fascia over the pectoralis major.

What it does

Lets the breast glide over the chest wall.

Key facts

Where: Loose areolar layer between the deep surface of the breast and the pectoral fascia
Function: Lets the breast glide on the chest wall; fixation of a tumour to it suggests deep invasion; subglandular implant plane

Relations

In front: Deep surface of the breast, covered by the deep layer of the superficial fascia
Behind: Pectoral fascia over the pectoralis major; laterally the fascia of the serratus anterior
Contents: Loose areolar tissue and fat, lymphatics and small perforating vessels from the internal thoracic artery and intercostal arteries

How to find it

Felt indirectly: a normal breast slides over the pectoralis major because of this loose fatty layer. In surgery it is entered by lifting the gland off the pectoral fascia, an almost bloodless plane except for perforating branches near the sternum.

Examination

With the hands pressed on the hips to tense the pectoralis major, the lump is moved parallel and across the muscle fibres; loss of the movement it had with the muscle relaxed means it is fixed to the fascia or muscle

On imaging

On mammography the retroglandular fat is the dark band in front of the pectoralis major; a good oblique view shows the muscle down to the level of the nipple. On MRI a preserved fat plane argues against invasion, while enhancement of the muscle signals it.

Common problems

A cancer that has grown across this layer and is fixed to the muscle or the chest wall is more advanced.
Breast implants sit either here (in front of the muscle) or under the pectoralis major.

How it is diagnosed

On examination, a lump that stops moving when the pectoralis is tightened suggests it is fixed; MRI shows whether the muscle is invaded.

Treatment

A mastectomy removes the breast along this layer, usually with the pectoral fascia.

Clinical notes

Subglandular (prepectoral) implants sit in this space, in front of the muscle; submuscular implants go under the pectoralis major
A tumour fixed to the chest wall (ribs, intercostal muscles or serratus anterior) is staged as more advanced; involvement of the pectoralis major alone does not count as chest wall invasion
Haematoma and seroma after breast surgery can collect in this plane

Test yourself

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

How is fixation of a breast tumour across the retromammary space tested?

With the hands pressed on the hips to tense the pectoralis major, the lump is moved; losing the movement it had at rest means it is fixed to fascia or muscle.

What role does the retromammary space play in mastectomy?

It is the plane where the breast is lifted off the chest wall; in a modified radical mastectomy the pectoral fascia is removed and the muscle kept.

Which lymph nodes do lymphatics reach after crossing the retromammary space?

The interpectoral (Rotter) nodes, between the pectoralis major and the pectoralis minor.

Where do subglandular breast implants sit?

In the retromammary space, in front of the pectoralis major; submuscular implants go under the muscle.

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

Its names

Official Latin (TA2): fascia pectoralis TA2 2317
Official Spanish (DeCS): Espacio retromamario
English (TA2): Pectoral fascia
Also called: fascia pectoralis superficialis

Sources: Terminologia Anatomica (TA2); Anatomy, Thorax, Breast; Anatomy, Thorax: Mammary Gland.

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Representative model, for educational purposes only.