Lymph nodes in the mammary gland may be caused by acute mastitis, lymphoma, breast cancer and other diseases. 1. Acute mastitis: patients may have breast pain, local redness, swelling, fever, enlarged lymph nodes, which is manifested as lymph nodes in the mammary gland, mostly occurring in postpartum breastfeeding women, mainly triggered by milk stagnation and bacterial invasion, endocrine disorders, etc., which is an acute suppurative infection of the mammary gland. 2. Lymphoma: Lymphoma is a malignant tumor originated from lymph nodes and lymphatic tissues, which can occur in the breast, and it is generally believed to be related to infection, immunity, physical and chemical factors and heredity, etc. It mainly manifests itself as painless lymph node enlargement, fever, night sweats and emaciation, etc. Patients will have the symptom of lymphatic nodes in the breast. 3. Breast cancer: when cancer cells metastasize through lymphatic vessels and block lymphatic vessels, it can also show symptoms of lymph node enlargement, as well as breast lumps, breast skin abnormality, nipple overflow and so on, and patients will show symptoms of lymph nodes in the breast. There are many reasons for lymph nodes in the breast, and it is recommended that patients go to the hospital in time to clarify the cause of the disease.