A 35-year-old woman has a slowly enlarging parotid mass. Histology shows epithelial ductal elements admixed with myoepithelial cells embedded in a chondromyxoid stroma. The tumor is classified as a 'mixed tumor' because it:

• A Contains both benign and malignant components
• B Arises from both ectoderm and mesoderm
• C Shows divergent differentiation into multiple germ cell layers
• D Has epithelial and mesenchymal-appearing elements derived from a single neoplastic cell type ✓

Explanation

In pleomorphic adenoma of the salivary gland, the mesenchyme-like chondromyxoid stroma is produced by neoplastic myoepithelial cells, so the entire tumor derives from one epithelial cell type showing divergent differentiation. This distinguishes it from teratomas, which arise from germ cells and contain elements of all three embryonic layers, making option C incorrect. Mixed tumors are almost always benign despite their heterogeneous appearance.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.