Page 402 - Concise Pathology for Exam Preparation ( PDFDrive )

14 The Oral Cavity and Gastrointestinal Tract 387

• Mucinous adenocarcinoma
• Oncocytic carcinoma
• Salivary duct carcinoma
• Adenocarcinoma; not otherwise specified
• Myoepithelial carcinoma
• Carcinoma expleomorphic adenoma
• Carcinosarcoma
• Metastasizing pleomorphic adenoma
• Squamous cell carcinoma
• Small-cell carcinoma
• Large-cell carcinoma
• Lymphoepithelial carcinoma

Mixed Parotid Tumour (Pleomorphic Adenoma)
• Accounts for more than 90% of the benign tumours of salivary glands
• Presents as painless swelling at angle of the jaw
• Most common location is superficial lobe of parotid followed by the submandibular
gland. It is rare in minor salivary glands.
• Most often diagnosed in the fourth to sixth decades of life, it is uncommon in children.
Women are more frequently affected.
• Thought to originate from epithelial/myoepithelial/ductal reserve cells.

Gross Morphology
• Small, well-demarcated, round and multilobulated lesion.
• Appears well encapsulated, but on close inspection shows finger-like extensions across
the tumour capsule at multiple sites.
• They are typically solid, but cut surface has a variegated appearance; may be grey-white,
myxoid, with blue, translucent pseudochondroid areas.
Microscopic Features (Fig. 14.1A and B)
• Pleomorphic adenomas show both epithelial and mesenchymal differentiation; were
also called mixed tumours because they were thought to arise from more than one germ
cell layer. They can undergo secondary malignant change.
• Epithelial component (ductal and myoepithelial cells) forms ducts, acini, tubules,
strands or sheets. Ductal cells are cuboidal; myoepithelial cells are flattened or spindled.
• Background stroma may be mucoid, myxoid, pseudochondroid or hyaline

Warthin Tumour
• Also called papillary cystadenoma lymphomatosum, it is a benign tumour seen exclu-
sively in the parotid gland.
• Usually affects males in the fifth to seventh decades of life.
• May be multicentric
• Histogenesis is disputed, but it is thought to arise from heterotopic salivary tissue
trapped in a regional lymph node during embryogenesis.
Gross Morphology
• Arises in superficial parotid gland; is small, round-to-oval, lobulated and encapsulated.
• Mucin-containing narrow cysts or cleft (slit)-like spaces showing papillary projections
may be seen on the cut surface.

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