An anomalous flexor digitorum sublimis muscle. A case report.

A report of an anomalous flexor digitorum superficialis muscle in a 14-year-old presenting as a painful, enlarging palmar mass was explored and found to lie on the ulnar side of the flexor, separate from the lumbrical. The anomalous flexor digitorum superficialis muscle was found attached to a normal flexor digitorum superficialis tendon supplied by a branch of the median nerve, and resected. The muscle represents a rare lesion to consider in diagnosis of hand masses. A phylogenetic anatomic explanation for the anomaly is feasible.