During a routine dissection for medical education, anatomists in China found something most people never learn they have: an extra muscle running down the front of the chest. The 70-year-old woman who donated her body had two of them, one on each side of the breastbone, and they did not match. At their upper ends, the muscles crossed with neck muscles in an X shape.
The muscle is called the sternalis. A team from Zhejiang Chinese Medical University in Hangzhou described the case in 2026 in the journal Folia Morphologica. The authors suggest that variants like this one could be mistaken for breast masses, interfere with heart tracings, and complicate chest or breast surgery.
