What Are the Causes of Breast Lumps and Swollen Arm Pit Nodes?

The breasts contain a number of specialized cell types that work together to allow lactation. The glandular tissue of the breast is made up of lobules and ducts, which produce milk and carry that milk to the nipple. Surrounding the glandular tissue are blood vessels, fat cells, connective tissue, and a series of lymph nodes that extend into the armpit. Lumps in the breast tissue or under the arm can indicate the presence of a number of disorders.

Ductal Carcinoma in Situ

Ductal carcinoma in situ develops within the ducts of the breast--the tissue that carries milk from the breast lobules to the nipple. Patients with ductal carcinoma in situ commonly develop a defined breast lump corresponding to the site of cancer development. The lump is usually visible on a mammogram and may be palpable in a physical breast examination. Although DCIS is not an typically invasive form of breast cancer, some patients diagnosed with DCIS also develop cancer growth in the lymph nodes, according to a study published in "The American Surgeon" in 2001. Patients with DCIS who develop swollen under-arm lymph nodes should seek medical attention.

Invasive Ductal Carcinoma

A defined lump in the breast combined with swollen lymph nodes may indicate invasive ductal carcinoma, a more aggressive form of ductal cancer 2. According to BreastCancer.org, invasive ductal carcinoma accounts for around 80 percent of breast cancer diagnoses 2. Patients with the disease develop a defined lump in the breast and also develop underarm lymph node swelling once the cancer reaches the lymph nodes. Invasive ductal carcinoma is diagnosed following a tissue biopsy to confirm cancer and may be treated with surgery, chemotherapy or radiation treatment 2. Doctors can effectively treat many cases of invasive ductal carcinoma, especially if cancer growth is detected early, so patients with breast and underarm lumps should seek medical attention to assess the health of their breasts 2.


In some cases, lumps in the breast and swollen lymph nodes under the arm could develop as a result of infections. Swollen lymph nodes alone can indicate a number of disorders, and patients with infectious diseases such as colds or coughs often can often feel swollen lymph nodes on the sides of the neck, in the groin and under the arm. An infection in the breast tissue, called mastitis, also leads to swollen lymph nodes as the body works to fight off the infection 3. MedlinePlus, a service of the National Institutes of Health, indicates that women with a breast infection may also develop a lump in the breast as fluid collects around the site of infection 3. Patients with a breast infection may also suffer from general feverish symptoms, as well as pain and itching of the affected breast 3. Breast infections can be treated with antibiotic medication and require immediate medical attention to prevent the formation of a breast abscess.