Prenatal diagnosis of exophytic nevus sebaceous of the scalp.

Nevus sebaceous is a complex hamartoma most commonly found on the scalp, face, and neck and is often present at birth, although some may be diagnosed later in infancy. We report the first prenatal diagnosis of isolated nevus sebaceous that presented at 19 weeks' gestation as a large and exophytic tumor of the scalp. This case emphasizes the crucial role of ultrasound examination performed with high-frequency probes, which revealed associated diffuse lesions of the face. Identification of such a facial involvement could have a dramatic prognostic impact.