I would like to add an image obtained from Spencer's publication [4] that can be very informative of this pathology.
Intact conjoined twins consist of two essentially complete fetuses united by one of eight anatomic sites, designated by the Greek root pagus, meaning “that which is fixed”. Ventral unions are categorized as cephalopagus (head to umbilicus), thoracopagus (thorax), and omphalopagus (abdomen); the less frequent dorsal unions are classified as craniopagus (cranial vault), rachipagus (vertebral column), and pygopagus (sacrum), being called ischiopagus (pelvis) the caudal unions, and parapagus (body side) the lateral ones.
A conjoined twin parasite is a grossly defective fetus, or fetal parts, attached externally (perhaps with internal connections as well) to a relatively normal twin (the autosite) in one of the same areas in which intact conjoined twins are united.
As can be seen in the image of Spencer's publication, taken from the book Pediatric Surgery by Ashcraft, et al, there are also 8 types of parasitic conjoined twins. The most complete answer of this case is "Pygopagus parasitic conjoined twins".
Intact conjoined twins consist of two essentially complete fetuses united by one of eight anatomic sites, designated by the Greek root pagus, meaning “that which is fixed”. Ventral unions are categorized as cephalopagus (head to umbilicus), thoracopagus (thorax), and omphalopagus (abdomen); the less frequent dorsal unions are classified as craniopagus (cranial vault), rachipagus (vertebral column), and pygopagus (sacrum), being called ischiopagus (pelvis) the caudal unions, and parapagus (body side) the lateral ones.
A conjoined twin parasite is a grossly defective fetus, or fetal parts, attached externally (perhaps with internal connections as well) to a relatively normal twin (the autosite) in one of the same areas in which intact conjoined twins are united.
As can be seen in the image of Spencer's publication, taken from the book Pediatric Surgery by Ashcraft, et al, there are also 8 types of parasitic conjoined twins. The most complete answer of this case is "Pygopagus parasitic conjoined twins".