Pleomorphic adenoma is usually arise from-
Pleomorphic AdenomaPleomorphic adenomas present as painless, slow-growing,mobile discrete masses. They represent about 60% of tumorsin the parotid, are less common in the submandibular glands,and are relatively rare in the minor salivary glands. Pleomorphicadenomas are benign tumors that consist of a mixture of ductal (epithelial) and myoepithelial cells, sothey exhibit both epithelial and mesenchymal differentiation.Epithelial elements are dispersed throughout thematrix, which may contain variable mixtures of myxoid,hyaline, chondroid (cailaginous), and even osseous tissue.In some pleomorphic adenomas, the epithelial elementspredominate; in others, they are present only in widelydispersed foci. This histologic diversity has given rise tothe alternative, albeit less preferred name mixed tumor. Thetumors consistently overexpress the transcription factorPLAG1, often because of chromosomal rearrangementsinvolving the PLAG1 gene, but how PLAG1 contributes totumor development is unknown.Pleomorphic adenomas typically manifest as rounded, well-demarcatedmasses rarely exceeding 6 cm in the greatestdimension. Although they are encapsulated, in some locations(paicularly the palate), the capsule is not fully developed,and expansile growth produces protrusions into thesurrounding tissues. The cut surface is gray-white and typicallycontains myxoid and blue translucent chondroid(cailage-like) areas. The most striking histologicfeature is their characteristic heterogeneity. Epithelial elements resembling ductal or myoepithelial cells are arrangedin ducts, acini, irregular tubules, strands, or evensheets. These typically are dispersed within a mesenchyme-likebackground of loose myxoid tissue containingislands of chondroid and, rarely, foci of bone (Fig. 14-6).Sometimes the epithelial cells form well-developed ductslined by cuboidal to columnar cells with an underlying layerof deeply chromatic, small myoepithelial cells. In otherinstances, there may be strands or sheets of myoepithelialcells. Islands of well-differentiated squamous epithelium alsomay be present. In most cases, no epithelial dysplasia ormitotic activity is evident. No difference in biologic behaviorhas been observed between the tumors composed largely ofepithelial elements and those composed largely of mesenchymalelements. Ref: Robbins Basic Pathology 9TH edition pg no 557
Parotid gland
Sub mandibular gland
Minor salivary gland
Superficial lobe
miscellaneous