Photo by laprimadonna
"Pectoralis" is Latin for "of the breast", and is derived from pectus ("breast, chest"). The pectoral structures take on various forms in the branches of the tree of life. For example, in the water, fish use their pectoral fins to help control their direction during swimming. In cetaceans (e.g. dolphins) pectoral fins are similar to the skeletal structure of land mammals, with fingers and ball and socket joints.
In humans, the pectoralis major is the main muscle of the anterior chest:
As discussed before, tears of this muscle occur almost exclusively in males, as a rule. Rules are made to be broken, however...
In this case, a 53 year-old female complained of severe shoulder pain after moving furniture over the weekend. Her clinical examination was confusing, and she was sent for an MRI for further evaluation. The alert MRI technologist noted edema along the anterior shaft of the humerus:
The MRI technologist then obtained additional axial images through the area in question, enabling visualization of a partial tear of the pectoralis major tendon at its humeral insertion:
An axial intermediate-weighted image better shows the anatomy of the partially torn pectoralis tendon (red arrow), the shaft of the humerus (yellow arrow), and the deltoid muscle (green arrows).
Tears of the pectoralis muscle and tendon are rare in women, and have been infrequently reported in the literature. In one example, a partial tear of the pectoralis major muscle masqueraded as a breast mass in an 87-year-old woman (Povoski and Spigos, Acta Radiologica 43, 615–616, 2002). The clinician may not consider this diagnosis. When edema is seen anterior to the proximal shaft of the humerus, additional axial MRI images should be obtained through the area, as in this case.