Midsternal bump: an infrequent localization of dermoid cysts

A 5-month-old boy was evaluated for an unusually large presternal bump present since birth. The ultrasound examination revealed a well-defined soft tissue mass with an oval shape. The lesion demonstrated a regular and well-demarcated outline, with an upper margin that was thinned and inserted into the upper skin plane; the content was anechoic with a small echogenic formation, mobile with changes in the patient's decubitus. The histologic diagnosis was dermoid cyst. Although dermoid cysts are commonly seen in the midline, the midsternal location, found in our patient, is rare. Dermoid cysts can have ultrasonographic features similar to those of other subcutaneous cystic masses. However, if an anechoic cyst with an internal well-circumscribed echogenic ball-like formation is seen within the presternal subcutaneous fat layer, as in our patient, dermoid cyst should be considered in the differential diagnosis of subcutaneous cystic masses.