Salivary Gland Tumors

What histological types of salivary gland carcinomas are distinguished in the modern classification?

Sources list the following histological types among salivary gland carcinomas and cancers:

• Mucoepidermoid carcinoma / mucoepidermoid cancer — the most common form of malignant epithelial salivary gland tumor.
• Adenoid cystic carcinoma / adenoid cystic cancer — the 2nd most common carcinoma of this localization; characterized by early perineural invasion.
• Acinic cell carcinoma / acinar cell cancer.
• Epithelial-myoepithelial carcinoma.
• Basal cell adenocarcinoma.
• Sebaceous adenocarcinoma.
• Papillary cystadenocarcinoma.
• Mucinous adenocarcinoma.
• Polymorphic low-grade adenocarcinoma.

Sources also list the following variants for carcinoma in pleomorphic adenoma: adenoid cystic carcinoma, mucoepidermoid carcinoma, undifferentiated carcinoma, and adenocarcinoma.

What benign salivary gland tumors exist?

Benign salivary gland tumors include various types of adenomas and papillomas. According to the classification, the following neoplasms are distinguished:

• Pleomorphic adenoma — the most frequent tumor.
• Myoepithelioma — a myoepithelial adenoma consisting of spindle-shaped, polygonal, and clear cells.
• Basal cell adenoma — composed of basaloid cells.
• Warthin tumor — adenolymphoma or papillary cystadenolymphoma.
• Oncocytoma — oncocytic adenoma.
• Canalicular adenoma.
• Sebaceous adenoma.
• Ductal papilloma.
• Cystadenoma.

Which benign salivary gland tumor is the most common?

The most common benign salivary gland tumor is pleomorphic adenoma. It accounts for 50% of all neoplasms in this location. Most frequently, this tumor arises in the parotid gland in individuals aged 50–60 years. Macroscopically, it is a node 1 to 6–10 cm in diameter, surrounded by a fibrous capsule, with a whitish-yellow or gray tissue on the cut surface.

What is the histological structure of Warthin tumor?

The histological structure of Warthin tumor (papillary cystadenolymphoma) is represented by glandular structures and cystic formations. The epithelial lining consists of a double layer of cells with eosinophilic granular cytoplasm, resembling oncocytes. Cells of the inner layer are columnar with apically located hyperchromatic nuclei. Papillary epithelial projections are identified in large cysts. Mucous cells and foci of squamous metaplasia may also be present. The tumor stroma is characterized by a prominent diffuse lymphocytic infiltrate with lymphoid follicle formation.

How does a mucocele differ from a true salivary gland retention cyst?

Sources do not provide a detailed histological comparison, but indicate the following clinical and morphological differences:

What is Küttner tumor and what is its pathogenesis?

Küttner tumor is listed in sources as Küttner tumor (inflammatory pseudotumor) and is cited among the synonyms for the term sialadenosis.

Sialadenosis is a dystrophic disease of the salivary glands developing secondarily against the background of various systemic pathologies of the body.

The pathogenesis is described in sources as the development of reactive-dystrophic changes in the salivary glands against the background of underlying diseases. Sialadenosis most frequently accompanies:

• diabetes mellitus;
• chronic prostatitis;
• blood disorders;
• thyroid disorders.

Additionally, in domestic classification, sialadenoses are designated as reactive-dystrophic changes in the salivary glands developing against the background of endocrine diseases and detected in patients with psychosomatic disorders.

Which pathological processes are classified as tumor-like lesions of the salivary glands?

Tumor-like lesions of the salivary glands include the following pathological processes:

• Sialadenosis (sialosis) — recurrent bilateral enlargement of the glands of a non-inflammatory and non-neoplastic nature.
• Oncocytosis.
• Necrotizing sialometaplasia — a combination of acinar necrosis and squamous metaplasia.
• Benign lymphoepithelial lesion (Mikulicz disease) — replacement of the parenchyma by a lymphoid cell infiltrate.
• Lymphoepithelial cysts of the parotid salivary glands — frequently accompany HIV infection and are regarded as a manifestation of persistent generalized lymphadenopathy.

What are the microscopic features of adenoid cystic carcinoma?

The microscopic features of adenoid cystic carcinoma depend on its histological variant:

• Cribriform variant — tumor cells form lattice-like structures due to multiple cysts lined by atypical ductal epithelium. Myoepithelial cells are located between the cysts. Ducts and cysts contain PAS-positive substance.
• Tubular variant — represented by duct-like structures with PAS-positive secretion and epithelial trabeculae surrounded by hyalinized stroma.
• Solid variant — represented by extensive fields of small cuboidal or oval epithelial cells. Nuclei are hyperchromatic, mitoses are present. Rare cribriform structures are encountered, often with central necrosis. Stroma is poorly developed.

What is Mikulicz disease and in which systemic diseases does it occur?

Mikulicz disease is described in sources as a condition characterized by slow, symmetrical, and painless enlargement of all major salivary and lacrimal glands. The secretory function of the glands is generally preserved, and complaints of xerostomia are absent.

Sources also indicate that benign lymphoepithelial lesion has the synonym Mikulicz disease. Its morphological features include:

• lymphoid cell infiltrate replacing the glandular parenchyma of the salivary gland lobules;
• proliferation of ductal epithelial and myoepithelial cells;
• formation of epithelio-myoepithelial islands replacing the intralobular ducts.

Associations and suspected factors according to sources:

• observed, in particular, in Sjögren syndrome;
• exact cause is unknown;
• suspected etiological factors: viral infection and systemic blood disorders, including Hodgkin lymphoma and leukemia.