Lobular

Lobular is an adjective used in anatomy and pathology to describe tissue that is organized into lobules, which are small lobes or subdivisions within an organ. The term comes from the Latin lobulus, meaning a little lobe.

In general anatomy, many organs have a lobular architecture, meaning their functional units are arranged as lobules separated by connective tissue septa. Examples include the breast, which contains terminal duct-lobular units that produce milk; the liver, where the functional units are hepatic lobules centered on a central vein; the pancreas and salivary glands, which also exhibit lobular organization. The term helps distinguish fine-grained, subunit structures from larger divisions.

In medical pathology, lobular describes tumors or lesions arising from lobular units. The most widely known example is invasive lobular carcinoma (ILC) of the breast, which often grows in single-file patterns due to loss of cell–cell adhesion (E-cadherin). There is also lobular carcinoma in situ (LCIS), a noninvasive condition that increases the future risk of breast cancer. Lobular patterns can also be described in other tissues, indicating a proliferation within the lobules rather than expanding from ducts or other structures.

Lobular should be contrasted with lobar, which refers to an entire lobe of an organ (for example, a lobar pneumonia affects an entire lobe of the lung). In both anatomy and pathology, lobular emphasizes small, subunit organization, whereas lobar refers to larger, whole-lobe regions.