The palmaris longus muscle has significant anatomical variance compared to other muscles of the upper extremity. The most frequent variation is the complete absence of the muscle, but a number of other variations exist. These variations include reversed, duplicated, bifid, or hypertrophied palmaris longus muscles. Anomalous muscles usually do not cause pathologic symptoms, but are a diagnostic dilemma. They become a surgical problem when they cause symptoms or are difficult to differentiate from soft-tissue masses. This article describes the presence of a reversed palmaris longus muscle in a 21-year-old man, diagnosed during exploration of the soft tissue mass on his right forearm.
