Isolated Unilateral Total Absence of the Pectoralis Minor Muscle: A Rare Finding in Two Cases

Anatomical variations are observed at times during a routine dissection process and some of them are clinically relevant as they can lead to certain clinical presentations or situations that are difficult to anticipate without the knowledge about their possibility. The unilateral non-syndromic complete absence of pectoral muscles is very rare. Their absence is always found to be associated with syndromes like Poland syndrome or Sprengel's deformity. During the routine anatomical dissection, we encountered two cases of non-syndromic complete unilateral absence of the pectoralis minor muscle. On further inspection of the cadaver in both the cases, no other bony (ribs, scapula), vascular, breast abnormalities, or muscular aplasia (fibers of the serratus anterior or pectoralis major) was noted. As the pectoralis minor muscle serves as the potential surgical landmark and can also be used as the myo-cutaneous flaps for facial reanimation surgeries and in thumb opponensplasty, the absence of the pectoralis minor muscle would come as a surprise for the surgeons during the process of harvesting the flap for these procedures, so the possibility of this kind of rare variation should be documented.