extralobular

Extralobular is an anatomical descriptor used to indicate a tissue or structure located outside a lobule. A lobule is a small, functionally discrete unit of a gland, consisting of secretory acini and the ducts that drain them; extralobular components are situated in the connective tissue between lobules or in ducts that originate outside a lobule. The term is commonly used in glandular anatomy and histology, including the breast, salivary glands, and pancreas, where ducts or duct systems can be classified as intralobular (within a lobule) or extralobular (outside a lobule).

In the breast, extralobular (interlobular) ducts drain several lobules and feed into the larger lactiferous ducts that convey milk to the nipple, whereas intralobular ducts lie within the lobules themselves. The distinction between extralobular and intralobular is a structural one that can aid pathologists and radiologists in describing the location and extent of lesions or developmental patterns.

Etymology: extralobular derives from Latin extra- meaning outside and lobulus meaning a small lobe. The term emphasizes position rather than function and is one of several locational descriptors used in glandular histology.