PLEOMORPHIC ADENOMA

PLEOMORPHIC ADENOMA

• Pleomorphic adenoma epithelial derived benign tumor whose cells demonstrate both mesenchymal and epithelial differentiation

• Synonym “mixed tumor” is given as it has mixture of epithelial and mesenchymal like elements and term pleomorphic adenoma is given due to its morphologic diversity

• Incidence : represents 45 to 74% of all the salivary gland tumors and 66% of all the benign tumors of salivary glands.

• Sites : Most common site is parotid.

  • next in  frequency is submandibular salivary gland

  • Intraoral site : common in hard palate than soft palate

  • Other locations are upper lip and mucosa

• Age and sex: can occur at any age with female preponderance

• Cell of origin : Epithelial origin. Mesenchymal components is derived from myoepithelial elements.

• Clinical features :

  • Slow growing nodular firm painless mass below and in front of the ear (superficial lobe)

  • presents as tonsillar fossa swelling if the deep lobe is involved

• Gross findings :

  • Irregular nodular mass with well defined borders

  • cut surface is homogenously tan to white with translucent zones representing myxochondroid and cartilaginous areas.

  • Hemorrhage and infarction can occur

• Microscopic findings:

  • It is composed of both epithelial and mesenchymal like components

  • Depending upon the proportions of mesenchymal like and epithelial elements pleomorphic adenomas are further subdivided into

    • Cellular type – predominantly epithelilal component

    • Myxoid type – predominantly myxomatous or myxochondromatous mesenchymal like elements

  • Tumor has well defined capsule (incomplete capsule in minor salivary glands)

  • Distinctive epithelial cell types are cuboidal, basaloid, spindle, clear squamous, plasmacytoid, oncocytic and sebaceous

  • Various cell patterns – trabecular, ductular or tubular, solid sheets and cystic structures

  • Myxoid, hyaline, chondroid and osseous areas constitute the mesenchymal like components

  • Crystalloids can be present

• Greater likelihood of malignant transformation is expected in tumors

  • with extensive hyalinization

  • occurrence in submandibular gland

  • older patient

  • larger tumorsize

• Immunohistochemistry

  • S-100 positive in both epithelial and stromal regions

  • Neoplastic myoepithelial elements are positive for calponin, CK 19 and smooth muscle specific protein

  •  GFAP activity inmyxoid areas

• Treatment

  • complete resection with parotidectomy or extracapsular dissection with a margin of normal tissue