Dr. Greene’s Answer:
Hemihypertrophy, also called hemihyperplasia, is a greater-than-normal asymmetry between the right and left sides of the body. It can occur as an independent condition (isolated hemihypertrophy) or as a part of a genetic syndrome (i.e. Beckwith-Wiedemann syndrome). Because hemihypertrophy is a disorder of the body’s normal controls of growth, it is not surprising that people with this condition can also have a higher rate of cancer.
In one study, 168 children with isolated hemihypertrophy were very carefully followed to try to determine the true rate of cancer in children with this condition. Just under 6% developed childhood tumors (American Journal of Medical Genetics, 1998; 79:274–278). The most common cancer is Wilms’ tumor (of the kidney), followed by adrenal carcinoma and liver cancer (hepatoblastoma).
Because most of the cancers occur in the abdomen, the recommendation has been made (by the participants of the First International Conference on Molecular and Clinical Genetics of Childhood Renal Tumors–among others) that children with hemihypertrophy receive a screening abdominal ultrasound every 3 months until age 7 and, at minimum, a careful physical examination every 6 months until growth is completed (I prefer ultrasound). One proposed exception to this recommendation is in hemihypertrophy due to Klippel-Trenaunay Syndrome– the risk of Wilm’s tumor does not appear to be increased in these cases (Pediatrics 2004; 113:326-329).
Some argue that screening for cancer in children with hemihypertrophy is not cost effective because most children do not get these tumors and, even for those who do, these tumors are fairly easy to treat even if caught late. Be that as it may, if it were my child, I would insist on the screening.