Final answer:
Rectal bleeding and diarrhea are less characteristic of cancer in children, especially kidney cancer, compared to symptoms like an asymmetrical abdomen, palpation of an abdominal mass, or a bone fracture without trauma.
Step-by-step explanation:
The least characteristic finding of cancer in children among the options given is rectal bleeding and diarrhea. While these symptoms can be associated with colorectal cancer, they are more commonly associated with gastrointestinal conditions rather than with renal or kidney cancer specifically. In contrast, asymmetrical abdomen, abdominal mass, and a broken bone without trauma (which could indicate a bone cancer or a cancer that has metastasized) are more typical signs of cancer in children. Notably, the observation of an asymmetrical abdomen and palpation determining an abdominal mass align with known cancer symptoms such as unusual lumps or swelling, which could signify the presence of a tumor. Additionally, bone pain or fractures without a clear cause can be indicative of a malignant process affecting the skeletal system.