What Are the Most Common Salivary Gland Tumors? A Review of WHO Classification

What Are the Most Common Salivary Gland Tumors? A Review of WHO Classification

Write in brief tumors of the salivary gland.
Answer:

WHO 2017 Classification of Salivary Gland Tumors

Malignant Tumors

• Mucoepidermoid carcinoma                       8430/3
• Adenoid cystic carcinoma                          8200/3
• Acinic cell carcinoma                                8550/3
• Polymorphous adenocarcinoma                8525/3
• Clear cell carcinoma                                  8310/3
• Basal cell adenocarcinoma                         8147/3
• Intraductal carcinoma                                 8500/2
• Adenocarcinoma, NOS                               8140/3
• Salivary duct carcinoma                             8500/3
• Myoepithelial carcinoma                              8982/3
• Epithelial – myoepithelial carcinoma            8562/3
• Carcinoma ex pleomorphic adenoma           8941/3
• Secretory carcinoma                                     8502/3
• Sebaceous adenocarcinoma                         8410/3
• Carcinosarcoma                                              8980/3
• Poorly differentiated carcinoma
  • Undifferentiated carcinoma                       8020/3
  • Large cell neuroendocrine carcinoma        8013/3
  • Small cell neuroendocrine carcinoma         8041/3
• Lymphoepithelial carcinoma                                   8082/3
• Squamous cell carcinoma                                        8070/3
• Oncocytic carcinoma                                                8290/3

Uncertain malignant potential

• Sialoblastoma                                                             8974/1

“Comparison of salivary gland tumor types in adults vs children”

Benign Tumors

• Pleomorphic adenoma                                                8940/0
• Myoepithelioma                                                           8982/0
• Basal cell adenoma                                                     8147/0
• Warthin tumor                                                              8561/0
• Oncocytoma                                                                8290/0
• Lymphadenoma                                                          8563/0
• Cystadenoma                                                              8440/0
• Sialadenoma papilliferum                                            8406/0
• Ductal papillomas                                                        8503/0
• Sebaceous adenoma                                                   8410/0
• Canalicular adenoma and other ductal adenomas      8149/0

Salivary gland tumors

“Pathophysiology of salivary gland tumors explained by the WHO”

Non-neoplastic Epithelial Lesions

• Sclerosing polycystic adenosis
• Nodular oncocytic hyperplasia
• Lymphoepithelial sialadenitis
• Intercalated duct hyperplasia

Benign Soft Tissue Lesions

• Hemangioma                                                                          9120/0
• Lipoma/sialolipoma                                                                 8850/0
• Nodular fasciitis                                                                       8828/0

“Emerging research on WHO-classified salivary gland tumors”

Haematolymphoid Tumors

• Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) – 9699/3

These new codes were approved by the IARC/WHO Committee for ICD-0.

WHO classification of salivary gland tumors

Secondary Tumors

Salivary Gland Description of Tumors of Salivary Gland

Pleomorphic Adenoma

• It presents as painless swelling at the angle of the jaw.
• The most common location is a superficial lobe of the parotid gland which is followed by the submandibular gland.
• The tumor is often diagnosed in the fourth to sixth decades of life and is uncommon in children.
• Females are more frequently affected.
• Grossly, pleomorphic adenoma is as mall, well-demarcated, round, and multilobulated lesion. Pleomorphic adenoma is typically solid but the cut surface has a variegated appearance; may be gray-white, myxoid with blue, translucent pseudochondroid areas.

Salivary Gland Microscopic Features

• Pleomorphic adenomas show both epithelial and mesenchymal differentiation
• Epithelial components, i.e. ductal and myoepithelial cells form ducts, acini, tubules, strands, or sheets. Ductal cells are cuboidal and myoepithelial cells are flattened or spindle shape.
• In pleomorphic adenoma background stroma can be mucoid, myxoid, pseudochondroid, or hyaline.

“Case studies on outcomes of WHO-classified salivary gland tumors”

Salivary Gland Warthin’s Tumor

• It is also known as papillary cystadenoma lymphomatous and is a benign tumor seen in the parotid gland.
• It affects males in the fifth to seventh decades of life.
• It is thought to arise from heterotopic salivary tissue trapped in a regional lymph node during embryogenesis.

Types of salivary gland tumors

Grossly it is small, round to oval, lobulated, and encapsulated. Mucin containing narrow cysts or cleft-like spaces showing papillary projections can be seen on the cut surface.

Salivary Gland Microscopic Features

• The tumor is composed of epithelial and lymphoid tissue.
• The lesion is an adenoma undergoing cyst formation with papillary projections in cystic spaces.
• Lymphoid matrix exhibit germinal centers.

“Impact of Warthin’s tumor on salivary gland health”

• A cyst is lined by a bilayered oncocytic epithelium, the inner cells of which are tall columnar with fine granular and eosinophilic cytoplasm and slightly hyperchromatic
  nuclei. The outer layer consists of basaloid cells.
• An eosinophilic coagulum is present within the cystic spaces.
• The numerous lymphocytic component may represent normal lymphoid tissue within which the tumor is developed.

Salivary Gland Monomorphic Adenoma

• It is similar to pleomorphic adenoma, except it does not contain a mesenchymal stromal component.
• This tumor is more common in minor salivary glands (For Example, upper lip), is bilateral in about 10% of cases.
• Various monomorphic adenomas are basal cell adenoma (most common), canicular adenoma, myoepithelioma adenoma, clear cell adenoma, membranous adenoma, and glycogen-rich adenoma.

Salivary gland tumor classification

“Advances in diagnosing salivary gland tumors with AI and WHO criteria”

Salivary Gland Mucoepidermoid Carcinoma

• It is the most common malignant tumor of the parotid gland and the second most common malignancy (adenoid cystic carcinoma is more common) of the sub-mandibular
  and minor salivary glands.
• Grossly some of the mucoepidermoid carcinomas appear well-circumscribed and may be partially encapsulated. Others are poorly defined and are infiltrative. The cut surface of the tumor may contain solid areas, cystic areas, or both. The cystic spaces contain viscous or mucoid material.

“Impact of the WHO on diagnosing mucoepidermoid carcinoma”

• Microscopically mucoepidermoid carcinoma is characterized by the presence of two types of cells, i.e. mucous cells and epidermoid squamous cells, the proportion of which helps to define the grade of the tumor, i.e. low grade (well differentiated), intermediate grade or high grade (poorly differentiated).
• The low-grade tumor has prominent cystic structures and proportionally more mucous cells, which may form gland-like structures and very few epidermoid cells.
• Intermediate-grade tumors show fewer cysts and a substantial solid component. There is an increasing proportion of epidermoid cells and occasional keratin pearl formation.
• High-grade carcinomas are solid tumors comprised mainly of epidermoid cells and show prominent cellular atypia and mitoses.

Salivary Gland Adenoid Cystic Carcinoma

• It is seen mainly in the fifth decade of life and presents as a gradually enlarging salivary mass, which can be accompanied by pain and paresthesia.
• Grossly, the tumor appears well-defied but unencapsulated. In the late stages, the tumor can be seen infiltrating the surrounding normal tissue. Adenoid cystic carcinoma is
  is solid in consistency and rarely displays cystic spaces on the cut surface.

“Importance of WHO classification in diagnosing salivary gland tumors”

• Microscopically the tumor consists of epithelial and myoepithelial cells variably arranged in tubular, cribriform, and solid patterns. The cribriform pattern is the most common and is easily recognizable.
• It is often referred to as the Swiss cheese pattern. Tumor cells are arranged in nests around cylindrical spaces that may contain a mucinous or hyalinized material.
• Cells that are arranged in layers and form ductal structures characterize tubular patterns. The solid pattern contains sheets of tumor cells with no intervening spaces.

Salivary Gland Acinic Cell Carcinoma

• It is a rare tumor that accounts for about l% of all salivary neoplasms.
• It is present in the fifth decade of life and is more common in women.
• The most common presentation is that of an asymptomatic enlarging mass.
• Grossly it demonstrates a mass that is well-circumscribed but lacks a true capsule.
• Microscopically it is a malignant neoplasm demonstrating serous acinar cell differentiation. Acinar cells are large, polygonal with lightly basophilic, granular cytoplasm and round, eccentric nucleus.