Sternalis muscle

Dr Henry Knipe and Radswiki et al.

The sternalis muscle is an uncommon anatomic variant of the chest wall musculature and is of uncertain aetiology and function. Its importance lies in that it should not be mistaken for a pathological lesion. 

Cadaveric studies have shown that the muscle is present in ~5% (range 1-8%) of both males and females and is twice as often unilateral as bilateral.

The sternalis muscle runs from the jugular notch inferiorly to approximately the caudal (inferior) aspect of the sternum. It is found adjacent to the medial edge of pectoralis major

The mammographic appearance of the sternalis muscle is variable. Typically it is visible in the medial aspect of the breast on the cranio-caudal mammogram and appears as a small soft tissue density/mass abutting the chest wall. Its margins and shape are variable (can range from flame shaped to an irregularly rounded density) 3. The muscle is usually not seen on the standard MLO or ML views. It typically measures 1-2 cm in maximum dimension.

As long as the radiologist is aware of the entity, there is usually little confusion. Ultrasound or CT or even MRI may be obtained for confirmation when the diagnosis is uncertain.

The sternalis muscle should be considered in the differential diagnosis if a posteromedial mass is noted on the CC view 2.

  • appears as a flat parasternal muscle, longitudinal in orinetation 6

In occasional situations, a "cleavage/valley view" may help to confirm bilaterality.

Thoracic anatomy
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Article information

rID: 12753
Section: Anatomy
Synonyms or Alternate Spellings:
  • Sternalis

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Cases and figures

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    Case 1
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    Case 2 - on mammogram
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    Case 3
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