Hi I'm 37 Yr Old Female . I Did A

Hi I'm 37 yr old female . I did a ct scan & my lhym nodle were swollen. The doctor send me some lab work also & the only adnolmal was Mononucleosis and my liver enlarge a bit. I also have a hernia wish was de reason for the ct , now the want to biopsy my lhym nodles for lynphoma . I'm worie & confuse already had done a pet/ct came out normal ? Can any of you explain me why they biopsy my lhym &, what they possible saw &, not telling me.
Thank you