Discussion of Sternalis muscle
- The sternalis is an uncommon anatomic variant of the chest wall musculature
- The sternalis is uncertain etiology and function.
- It runs from the infraclavicular region inferiorly to approximately the caudal aspect of the sternum in a superficial location.
- It is the superficial location of the muscle that allows for its occasional inclusion in the medial aspect of the craniocaudal mammogram.
- Cadaveric studies have shown that the muscle is present in approximately 8% of both males and females
- Sternalis is twice as often unilateral as bilateral.
- Sternalis should not be confused with a pathological process.
- CT may be obtained for confirmation when the diagnosis is uncertain.
 Imaging Findings for Sternalis muscle
- The mammographic appearance of the sternalis muscle is variable.
- Visible in the medial aspect of the breast on the craniocaudal mammogram
- It typically measured 1-2 cm in maximum dimension.
- Appeared as a density of varying irregularity with an ill-defined margin.
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 References for Sternalis muscle
- Bradley, FM, Hoover, HC, Jr, Hulka, CA, Whitman, GJ, McCarthy, KA, Hall, DA, Moore, R, Kopans, DB. The sternalis muscle: an unusual normal finding seen on mammography. Am. J. Roentgenol. 1996 166: 33-36.