Benign Neoplasms (Adenomas)
The morphological pattern of benign lesions features a diverse cellular composition and stromal architecture. They are most frequently localized in the parotid gland.
- Pleomorphic adenoma: Characterized by a complex structure. Epithelial cells form trabeculae and ducts with cysts, embedded in a mucin-like (myxoid) substance. A distinctive feature is the presence of chondroid (cartilage-like) areas and numerous myoepithelial cells forming networks.
- Myoepithelial adenoma: Identified predominantly in women aged 40–80 years. It presents as a firm, whitish node. Composed of spindle-shaped, polygonal, plasmacytoid, or clear cells forming cords against a myxoid or hyalinized matrix. Three variants are distinguished: solid, reticular, and mixed.
- Basal cell adenoma: In 80% of cases, it affects the parotid gland. It is an encapsulated node consisting of basaloid cells forming solid, trabecular, tubular, or membranous structures within a poorly developed fibrous stroma.
- Warthin tumor (papillary cystadenolymphoma): A rare tumor (about 6%) affecting men over 40 years of age. Cross-section reveals cysts with serous content and papillary projections. The epithelium is bilayered (inner layer comprises columnar cells with apical hyperchromatic nuclei and eosinophilic cytoplasm, similar to oncocytes). The stroma is heavily infiltrated by lymphocytes with lymphoid follicle formation.
- Oncocytoma: A very rare adenoma originating from differentiated epithelial cells of the striated duct.
Malignant Epithelial Tumors (Carcinomas)
Malignant forms account for a significant proportion of pathologies (up to 46%). The most common among them is mucoepidermoid carcinoma. It arises predominantly in women in their 5th–6th decades of life.
The grade of mucoepidermoid carcinoma directly determines the prognosis (along with surgical radicalism and depth of invasion):
- Low-grade: Dense, fixed nodes. Cellular polymorphism, pathological mitoses, marked stromal hyalinosis. Secretory cells are solitary.
- Intermediate-grade: Composed of epidermoid and mucus-secreting cells. Microfoci of necrosis and focal hyalinosis are present.
- High-grade: Lacking cellular polymorphism and necrosis. Characterized by an abundance of macrocysts and secretory cells.
Adenoid cystic carcinoma (cylindroma) is the second most frequent (1.2–10%). A favored localization is the minor salivary glands of the palate. The tumor grows slowly but aggressively: early perineural invasion is characteristic. The cribriform (sieve-like) variant contains PAS-positive substance within cysts, while the solid variant (if comprising more than 30% of the tumor) indicates an extremely unfavorable prognosis.
Other significant forms:
- Acinic cell carcinoma: A slowly growing, encapsulated tumor with basophilic cytoplasmic granularity. Prognosis depends on invasion, and unpredictable hematogenous metastases to the lungs are possible.
- Carcinoma ex pleomorphic adenoma: Accounts for 15–20% of all malignant salivary gland neoplasms. Regardless of the subtype (most commonly adenoid cystic or mucoepidermoid carcinoma), it is characterized by necrosis, hemorrhage, and stromal hyalinosis.
IHC marker triad for myoepithelial adenoma: CAS — Cytokeratin, Actin (smooth muscle), S-100 protein.
Class and exam questions
What factors determine the prognosis in mucoepidermoid carcinoma?
Prognosis depends (in descending order of significance) on the radicalness of surgical resection, tumor differentiation grade, and depth of invasion.
What are the clinical distinguishing features of adenoid cystic carcinoma?
It tends to undergo early perineural invasion, which manifests as severe pain even when the tumor is small.
What is characteristic of the Warthin tumor stroma?
The stroma of papillary cystadenolymphoma is typically characterized by a pronounced diffuse lymphocytic infiltrate with the formation of well-developed lymphoid follicles.
What else to study on this topic
- Clinical and Morphological Forms of Obstructive Salivary Gland Diseases
- Pathogenesis and Morphogenesis of Reactive Pulp Changes in Dental Caries
- Complications of Apical Periodontitis
- Clinical and Morphological Characteristics of Odontogenic Tumors and Jaw Cysts
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