Summary of "Pleomorphic Adenoma"

Summary of Scientific Concepts and Discoveries

Pleomorphic Adenoma (PA):
- Most common benign salivary gland tumor, primarily affecting the parotid glands.
- Composed of epithelial and myoepithelial cells within a stroma that exhibits various mesenchymal components.
Structure of Salivary Glands:
- Secretory cells: Serous and mucous cells.
- Secretory end pieces: House secretory cells and are connected to the main excretory duct through intermediary ducts.
- Ductal cells line the ducts, which include intercalated and striated ducts leading to the excretory duct.
- Myoepithelial cells: Stellate-shaped contractile cells that assist in saliva secretion.
Tumor Composition:
- Neoplastic epithelial or ductal cells and myoepithelial cells.
- Mesenchymal metaplasia can lead to various tissue types (e.g., chondroid, myxoid, chondromyxoid, osseous, and adipose tissue).
Terminology Clarification:
- "Pleomorphic" refers to the mixture of epithelial and mesenchymal tissue types, not atypical cells.
- Historically referred to as a "mixed tumor," but derived from mesenchymal metaplasia rather than multiple germ layers.
Genetic Alterations:
- Cytogenetic studies reveal gene alterations in PLAG1 and HMGA2 on chromosomes 8 and 12.
Epidemiology:
- Most common in females and typically occurs in individuals aged 40-60.
- Symptoms include slow-growing, painless swelling, primarily in the superficial lobe of the parotid gland.
Histological Features:
- Ductal epithelial cells: Cuboidal, proliferating in ducts, tubules, or sheets with eosinophilic secretions.
- Myoepithelial cells: Spindle-shaped or polygonal/oval with eosinophilic cytoplasm.
- Varied stroma: Myxoid to fibrous, sometimes hyalinized with mesenchymal elements.
Treatment:
- Surgical Excision is the preferred treatment for both major and minor Salivary Glands, emphasizing the importance of preserving the facial nerve during parotid gland surgery.