This case was pathologically proven as a teratoma.
This kind of tumour shows mixed dermal elements derived from the three germ cell layers.
The majority of teratomas present congenitally in the sacrococcygeal region, within the ovaries of adolescent females and the testes in young men.
Extragonadal teratomas tend to occur in midline structures in the anterior mediastinum, retroperitoneum, sacrococcygeal region, and pineal gland.
Retroperitoneal teratomas have two incidence peaks: first six months of life and in early adulthood.
There is a 25% chance of malignancy.