Intra-abdominal masses may be benign or malignant Children are often asymptomatic even when the tumor is large; frequently, the mass is detected by the caregiver noticing a protuberant or lopsided abdomen It is difficult to feel an intra-abdominal mass, as well as outline its limits and its degree of mobility, if an infant or child is crying After allowing the child to calm, the physician should make an effort to palpate the intra-abdominal contents carefully These masses can be fragile and prone to rupture; therefore, palpation of the mass should be done gently and strictly limited to as few examiners as possible Retroperitoneal masses tend to be fixed, whereas masses attached to the mesentery or omentum are mobile and may be shifted to different locations by the examiner Pelvic masses are commonly fixed and often can best be felt by rectal examination A presacral mass may narrow the rectum and produce constipation Abdominal masses present with various characteristics and may be smooth, nodular, cystic, or firm