During prenatal ultrasound, an<unk>  having an external component may appear as a fluid-filled cyst or a solid mass sticking out from the fetus' body. Fetal<unk> s that are entirely internal may be undetected if they are small; detection (or at least suspicion) is possible when the fetal bladder is seen in an abnormal position, due to the<unk>  pushing other organs out of place. At birth, the usual presentation is a visible lump or mass under the skin at the top of the buttocks crease. If not visible, it can sometimes be felt; gently prodded, it feels somewhat like a hardboiled egg. A small<unk> , if it is entirely inside the body, may not present for years, until it grows large enough to cause pain, constipation and other symptoms of a large mass inside the pelvis, or until it begins to extend out of the pelvis. Even a relatively large<unk>  may be missed, if it is internal, because the bony pelvis conceals and protects it. Mediastinal tumors, including<unk> s, are similarly concealed and protected by the rib cage. Some<unk> s are discovered when a child begins to talk at about age 2 years and complains of their bottom hurting or feeling "poopy" when they ride in a car seat. Other tumors can occur in the<unk>  and/or presacral regions and hence must be ruled out to obtain a differential diagnosis. These include extraspinal ependymoma, ependymoblastoma, neuroblastoma and rhabdomyosarcoma. Smaller<unk> s with an external component, seen in prenatal ultrasounds or at birth, often are mistaken for spina bifida. Cystic<unk>  and terminal myelocystocele are especially difficult to distinguish; for more accurate diagnosis, MRI has been recommended.
Sacrococcygeal teratoma
Myxoid cyst
Gonadoblastoma
Pineal gland cyst
Ectopic testis
Luteoma
Chordoma
Hydrocele testis