Can ultrasound detect cancer in lymph nodes?

It depends: Ultrasound is commonly used to check the condition of the lymph nodes. But the results are dependent on the experience of the sonographer(radiologist). A good sonographer can tell if a lymph node is benign or suspect for Cancer. The final answer(to be 100% certain) requires a biopsy of a suspicious lymph node(if it is enlarged to 1cm or more in size)

No...: Will only show enlargement or structural anomaly. Need a biopsy for detection of cancer.