Each breast contains a number of cell and tissue types that support the structure and function of the breast. The glandular tissue of the breast, which produces and secretes milk, consists of ducts and lobules. Surrounding the glandular tissue are fat cells, connective tissue, nerves, blood vessels and lymph nodes, all of which support the health of the breast. Breast lumps, a result of the uncontrolled proliferation of breast cells, often develop within distinct regions of the breast.
Ducts
A very common site for breast lump growth is the milk duct, a tube that connects a milk-producing lobule to the nipple. Each breast contains several ducts that connect to a number of lobules, forming a tree-like structure within the breast. Breast lumps in the duct may affect only one duct, or may affect a group of ducts as the breast lump grows.
Breast lumps in the ducts may be benign or malignant. Benign, non-cancerous lumps include intraductal papillomas, while malignant duct breast lumps may include localized or invasive ductal carcinomas, according to MedlinePlus. Ductal breast lumps commonly present as a palpable lump and can be detected on a mammogram or during a clinical physical examination. Following diagnosis, the treatment for a duct lump may include surgery, radiation, hormone therapy or chemotherapy, depending on the severity of the growth.
Lobules
Another common site of breast lumps is a breast lobule. Each lobule contains a series of cells arranged in bulb-like clusters called acini, and each cell produces milk proteins it expels into an attached breast duct. Lumps within the lobules typically feel like a thickening of the breast tissue rather than a defined lump, and the lump can be detected on a mammogram. Benign lumps in the lobule include lobular carcinoma in situ, a non-cancerous growth that can slightly increase the future risk of breast cancer, according to the Stanford Medicine Cancer Center. Malignant lumps in the lobules are called invasive lobular carcinomas and may affect one or more breast lobules. The treatment for lobular breast lumps may consist of surgery, radiation therapy, chemotherapy or hormonal therapies.
Fat Tissue
Occasionally, lumps within the breast will affect the connective tissue surrounding the glandular tissue rather than the gland tissue itself. Tumor growth within the fat tissue is called a lipoma, a type of soft tumor made up of fatty tissue, according to MedlinePlus. Lipomas can occur in many areas of the body, including the breast. Penn State University Milton S. Hershey Medical Center describes a lipoma as a soft, rubbery growth that can be felt under the skin. The medical center indicates that women are more prone to lipoma under the skin, such as in the breasts, and that the risk of developing a lipoma increases in overweight individuals. Not all lipoma breast lumps require treatment, but large or painful lumps can be removed with surgery.
