When the unexpected happens: educational reflections on and values of dissection of a cadaver with multiple anatomical variations

Anatomical variations observed during cadaveric dissection provide important clinical insights and reinforce the teaching of both normal anatomy and the range of variation that clinicians may encounter in practice. Understanding these anatomical variations is essential for medical education and clinical practice, particularly in surgical and diagnostic procedures. During routine dissection of a Caucasian female cadaver in her 60s, we identified three rare ipsilateral right-sided anatomical variations involving the brachial plexus, pectoralis major muscle, and rectus abdominis muscle, using standard dissection methods and systematic documentation. The first finding was complete absence of the musculocutaneous nerve, accompanied by compensatory median nerve enlargement (diameter increased from 4.14 mm to 6.05 mm), which provided innervation to the anterior arm muscles; notably, no functional muscle atrophy was observed, indicating successful neural compensation. The second variation involved the right pectoralis major muscle, which showed an atypical configuration with one clavicular head and two distinct sternocostal divisions arising separately from the manubrium and sternal body. The third finding was a well-circumscribed abdominal wall defect at the right second tendinous intersection of the rectus abdominis muscle, with bowel herniation through the defect; the defect measured 26.42 mm in diameter. This case illustrates the educational value of cadaveric dissection in revealing rare anatomical variations with significant clinical implications, particularly the unusual ipsilateral coexistence of these findings. Although a common developmental explanation remains conjectural, recognition of such variants is essential for clinicians to prevent diagnostic errors and surgical complications, underscoring the enduring importance of anatomical dissection in medical curricula.