Swollen groin lymph nodes

Yesterday I took my 16 yr old daughter to the surgeon about a "hernia" that a previous Dr. diagnosed.  The surgeon said it was unlikely a hernia because he felt other swollen nodes around it. They are on the left side between the pubic line and the hip bone.  There is one lymph node that is painful and about an inch in length and 1/2 inch wide (approx.)  I wasn't aware of the others until he told us.  He has scheduled a biopsy in 23 days, he is giong to be on vacation which is why they are scheduling so far out.  

He explained they are going to put her under a local and numb the area while they do the biopsy.  I know that she's had it for at least a month and half.  In the beginning of May she did have her tonsils and adnoids removed, but she said the lump was there before that.. only smaller.  

What type of infections can cause this type of enlarged lymph node?  How do you tell the difference between an infection or cancer?  

Thanks, from a very worried mother.

[DrNoopurMD]

Hi,

Infections like sore throat, tonsillitis, dental infection, syphilis, genital herpes to name a few can all cause enlarged lymph nodes.
To know the difference between cancer and infection a biopsy is essential and diagnostic.
What other symptoms does your daughter have apart from swollen lymph nodes?