Becker nevus with an underlying desmoid tumor: a case report and review including Mayo Clinic's experience.

Background: Becker nevus is a nevoid melanosis, referred to as Becker nevus syndrome when it is associated with other anomalies. Our objectives were to report the occurrence of a Becker nevus with an underlying desmoid soft-tissue tumor; to review Mayo Clinic's experience with Becker nevi, concentrating on Becker nevi associated with bone, vascular, neural, and other soft-tissue abnormalities; to inform physicians of the Becker nevus syndrome; and finally to alert clinicians to evaluate a Becker nevus with its associations in mind.

Observations: A 46-year-old woman had a Becker nevus with an underlying desmoid-type fibromatosis (desmoid tumor) presenting clinically as a "painful dimple" within the nevus. Review of medical records for 1997 through 2006 at Mayo Clinic, Rochester, Minnesota, yielded 52 patients with Becker nevi, 12 of whom had an associated bone, vascular, neural, congenital, or other soft-tissue abnormality, ranging from liposarcoma to an accessory areola.

Conclusions: We add to the literature a unique case of desmoid-type fibromatosis immediately beneath a Becker melanosis, which presented as a painful dimple. We hope to raise awareness that a Becker nevus may be associated with other abnormalities, including an infiltrative soft-tissue tumor. We also emphasize the importance of follow-up, including inspection of not only the surface but also the deep tissues underlying the Becker nevus.