Thank you for the information,
There are some common causes of such enlarged lymph nodes.The common ones are infection, abscess, cancer, immune disorders, skin infection, hodgkin and non-hodgkin lymphoma, etc.
The chances of infectious cause are less since you do not have any symptoms and it is for a long time for many years.The breast cancer has already been screened by mammography.
You should rule out the other causes and have the relevant investigations done like blood counts, FNAC/biopsy of the lymph nodes, licer and chest ct scan, etc. to know the associated abnormality.
The lymphoma should be ruled out as it may occur at any age.The lymphoma is the most common type of blood cancer in the United StatesThe non-hodgkin lymphoma usually occurs at older age.The incidence of lymphoma is approx 1 in 4466 people in US.
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incidence of lymphoma
Let me know if you have any doubt.