An 11-year-old girl was hospitalised because of a large mass in her back (figure 1). She was the second child in her family where there was neither twin pregnancy nor fetal malformation. The large mass has two parts where the upper part consists of a mammary gland and an attached upper limb including a scapular, humerus and two fingers, and where the lower part contains a thick-walled sac which endlessly secreted mucosal …