Palmaris longus is a short fusiform muscle, the origin of this muscle is from the medial epicondyle of the humerus and inserts in the wrist at the palmar aponeurosis superficial to the level of the flexor retinaculum.
Variant anatomy is described in the literature and can include anomalous origin, course and/or insertion. Such variants also include duplication, digastric, and entirely muscular or proximal tendinous and distal muscular (i.e. reverse palmaris longus).
Palmaris longus anomalies can present with median nerve compression symptoms that are indistinguishable from symptoms due to other masses.
The radiologist should be familiar with these anomalies to prevent unneeded surgery.