i had a similar experience it took someone saying about the racquetball sized lump in my neck “that looks bad you should have someone look at that” to go get it checked i had stage3 hodgkin’s i also was perfectly healthy except for the cancer 6 months of godawful chemo and i’ve been in remission 20 years now   side note i’ve always believed stress caused it   best wishes it’s definitely a life altering experience