Final answer:
A lymph node biopsy is performed to examine enlarged lymph nodes for cancerous cells; it involves the surgical removal of part or all of a lymph node for analysis.
Step-by-step explanation:
Your brother likely underwent a procedure called a 'lymph node biopsy,' which is typically performed when there is an enlarged lymph node that does not return to normal size and may be indicative of an underlying condition, such as lymphoma. During a lymph node biopsy, a surgeon may remove all or part of the lymph node to examine the tissue for the presence of cancerous cells. The biopsy is an important diagnostic tool that helps doctors to determine the appropriate course of treatment following the analysis of the tissue sample.