BACKGROUND: Klippel-Trenaunay-Weber syndrome is a rare congenital soft tissue anomaly with sporadic occurrence characterized by the triad of multiple hemangiomas, arteriovenous fistulas and unilateral limb hypertrophy.
CASE: A 27-year-old, pregnant woman was referred at 31 2/7 gestational weeks. On prenatal sonography, multiloculated cystic areas involving the left side of the thorax and hypertrophy of the upper portion of the left arm were diagnosed without diagnostic findings on color flow Doppler studies of the cutaneous hemangioma. There was no progression within the remainder of the gestational period, and the neonatal outcome was good.
CONCLUSION: Klippel-Trenaunay-Weber syndrome should be considered in the differential diagnosis of a fetal thoracic mass even if color flow Doppler studies of the mass are negative.