Polymorphous low-grade adenocarcinoma (PLGA) is a rare tumor of the salivary glands that is limited, to a great extent, to the minor salivary glands and commonly, but not exclusively, localized in the palate of the mouth. The major salivary glands are the parotid glands (at the side of the face, below the ears), the sublingual glands (below the tongue), and the submandibular glands (below the lower jaw). As the name suggests, each of the major salivary glands is of substantial size and visible to the naked eye. There are about 600 to 1,000 minor salivary glands that are microscopic in size. These minor salivary glands are found in the lining (mucosa) of the lips, tongue, and hard and soft palate, as well as inside the nose, cheeks, and sinuses.
Less than one (1%) per cent of all cancers reported in the USA are salivary cancers and, of these, 80% begin in the parotid glands, and about 15% begin in the submandibular glands, leaving only 5% that begin in the sublingual and minor salivary glands. Most of the tumors that start in the major salivary glands turn out to be benign, while most, but not all, of the cancers that start in the minor salivary glands turn out to be malignant.