BENIGN TUMOURS

OF THE SALIVARY

GLANDS

Dr Preeti Sharma, MDS

Associate Professor

Dept of Oral & Maxillofacial Pathology & Oral

Microbiology,

Subharti Dental College & Hospital

Swami Vivekanand Subharti University

Meerut, UP

What you will Learn

Histogenesis of salivary gland neoplasms

Classification of salivary gland tumours

Benign salivary gland tumours:

A. Pleomorphic adenoma

B. Myoepithelioma

C. Warthin’s Tumor

D. Basal cell adenoma

D. Oncocytoma and Oncocytosis

E. Canalicular adenoma

Tumors of salivary glands constitute a heterogeneous group of lesions of great morphologic variation.

These tumors are relatively uncommon

HISTOGENESIS OF SALIVARY GLAND NEOPLASMS

Semipluripotential bicellular reserve cell hypothesis

Specific reserve or basal cells of the excretory and intercalated ducts or both are responsible for replacement of all types of cells in normal gland and hence are the sole source for neoplastic transformation.

Multicellular histogenetic concept

Any of the various cells found in the normal salivary gland could serve as a precursor for neoplasia; thus, this is a multicellular histogenetic concept.

Myoepithelial cell is responsible for the morphologic diversity of the tumour like pleomorphic adenoma (including the production of the fibrous, mucinous, chondroid and osseous areas

Intercalated duct reserve cell can differentiate into ductal and myoepithelial cells which can undergo mesenchymal metaplasia

HISTOLOGICAL CLASSIFICATION OF SALIVARY GLAND TUMORS (WHO, 2005)

1. BENIGN EPITHELIAL TUMOURS

Pleomorphic adenoma

Myoepithelioma

Basal cell adenoma

Warthin tumour

Oncocytoma

Canalicular adenoma

Sebaceous adenoma

Sebaceous adenoma

Sebaceous lymphadenoma

Ductal papilloma

- Inverted ductal papilloma

-Intraductal papilloma

-Sialadenoma papilliferum

Cystadenoma

- Papillary cystadenoma

- Mucinous cystadenoma

2. MALIGNANT EPITHELIAL TUMOURS

Acinic cell carcinoma

Mucoepidermoid carcinoma

Adenoid cystic carcinoma

Polymorphous low grade adenocarcinoma

Epithelial-myoepithelial carcinoma

Basal cell adenocarcinoma

Sebaceous carcinoma

Sebaceous lymphadenocarcinoma

Cystadenocarcinoma

Low-grade cribriform cystadenocarcinoma

Mucinous adenocarcinoma

Oncocytic carcinoma

Salivary duct carcinoma

Adenocarcinoma, NOS

Myoepithelial carcinoma

Malignant Mixed Tumors

A. Carcinoma ex pleomorphic adenoma

B. Carcinosarcoma

C. Metastasizing pleomorphic adenoma

Squamous cell carcinoma

Small cell carcinoma

Lymphoepithelial carcinoma

PLEOMORPHIC ADENOMA Benign mixed tumor WILLIS

Most common benign neoplasm of salivary gland

Parotid gland most common site.

Approximately 8% of PA involve the minor salivary glands, the palate is the most common site (60-65%) of minor salivary gland involvement.

PATHOGENESIS

Mixed tumor

Morphologic complexity

Numerous theories

Myoepithelial & reserve cells

Ultrastructural studies have confirmed the presence of both ductal & myoepithelial cells in pleomorphic adenomas

Histogenesis

Myoepithelial cell is responsible for the morphologic diversity.

Intercalated duct reserve cell can differentiate into ductal & myoepithelial cells.

myoepithelial cells can undergo mesenchymal metaplasia

Clinical features

Parotid gland (90%)

Intraoral accessory salivary gland

Female male ratio 6:4

4th – 6th decades

Painless nodule

Pleomorphic adenoma of parotid gland

Irregular nodule, firm consistency, no fixation

Cystic degeneration

Skin seldom ulcerates

Pain not common

Facial paralysis

Pleomorphic adenoma of intraoral accessory glands (size1-2cm)

Difficulty in mastication, talking, breathing

Lips (20%) buccal mucosa (10%)

Palatal (60%) Pleomorphic adenoma fixed

Pleomorphic adenoma of parotid gland does not show fixation

Recurrent PA

Possible reasons for recurrences in PA include:

• Diffluent nature of the predominantly mucoid tumors.

• Variability of the thickness of the capsule, together with the tendency of the tumor to invade the capsule.

• Tumor protuberances bulging through the

capsule.

• Intratumoral splitting beneath the capsule.

• It is probable that tumor cells have low biological requirements and this enables them to survive when split into the operative side.

HISTOLOGIC FEATURES

Greater variation

Diverse histologic pattern

Cuboidal cells in tube or duct like structures

Proliferation of epithelium, in strands or sheets or cords

Stellate polyhedral or spindle form

Squamous epithelial cells

Exhibits typical intercellular bridge & keratin pearls

Loose myxoid material

Foci of hyalinised connective tissue or cartilage like material

Mucoid material

Encapsulated

The highly characteristic ‘stromal’ changes are believed to be produced by the myoepithelial cells.

Extensive accumulation of mucoid material may occur between the tumor cells, resulting in a myxomatous background.

Vacuolar degeneration of cells in these areas can produce a chondroid appearance.

In many tumors, the stroma exhibits areas of an eosinophilic, hyalinized change. At times, fat or osteoid also is seen.

Foote & Frazell ( 1954) categorized into following types:

Principally myxoid

Myxoid & cellular components present in equal proportion

Predominantly cellular

Extremely cellular

Cellular adenoma

Myoepithelioma

Carcinoma ex Pleomorphic Adenoma

Treatment

Surgical excision

Intraoral lesions conservatively by extracapsular excision

Differential Diagnosis

WARTHIN’S TUMOR (Papillary cystadenoma lymphomatosum)

♠ Benign neoplasm

♠ Second most common tumor in the salivary glands.

♠ Exclusively in the parotid gland

♠ Less common than pleomorphic adenoma.

Pathogenesis-

Delayed hypersensitivity disease.

Lymphoid component of the tumor is an exaggerated secretory immune response.

A strong association between development of this tumor and smoking documented.

EB virus also implicated in the pathogenesis of this tumor.

Arise from heterotopic salivary gland tissue found within parotid lymph nodes.

May develop from a proliferation of salivary gland ductal epithelium.

Slowly growing mass of parotid gland

Firm or fluctuant to palpation.

Most frequently occurs in the tail of parotid near the angle of the mandible.

Occurs bilaterally in 5% to 14% of cases.

Occurs rarely in submandibular & minor salivary glands

Clinical Features

Older adults

6th -7th decades

Male predilection but recent studies show substantial percentage of patients who are women.

Solitary cyst

surrounded

by solid,

white,

homogenous

tissue

representing

the lymphoid

component.

Multicystic pattern

with multiple white

nodules

throughout which

is lymphoid

component

HISTOPATHOLOGIC FEATURES

One of the most distinctive histopathologic patterns of any tumor in the body.

Mixture of ductal epithelium & lymphoid stroma

Epithelium is oncocytic in nature, forming uniform rows of cells surrounding cystic spaces.

Cells arranged in two layers :

• Inner layer with tall columnar cells with centrally placed, palisaded and slightly hyperchromatic nuclei.

• Second layer of cuboidal cells with more vesicular nuclei.

Lining epithelium shows multiple papillary infoldings that protrude into cystic spaces.

Focal areas of squamous metaplasia

Epithelium supported by a lymphoid stroma that shows germinal centre formation

Treatment Surgical removal

Local resection

6% - 12% malignant transformation

Papillary cystic tumor with

a lymphoid stroma

Myoepithelioma

Uncommon

Accounts for less than 1% major & minor tumors

Clinical features

Occurs in adults with equal gender distribution

Parotid gland most commonly involved.

Palate is the most frequent intraoral site of occurrence.

HISTOLOGIC FEATURES

Exclusively of neoplastic myoepithelial cells.

Neoplastic cells are predominantly spindle–shaped or plasmacytoid.

Epithelioid or clear cells may also be present.

When spindle cells predominant, tends to be more cellular.

Ultrastructural identification of myoepithelial cells required.

Treatment

Surgical excision.

MONOMORPHIC ADENOMA

A more uniform histopathologic pattern than the common pleomorphic adenoma.

Group of benign salivary gland tumors

OXYPHILIC ADENOMA (Oncocytoma)

Rare benign tumor.

Occurs in parotid gland

More common in females

Elderly persons.

Tumor appears as a firm mass that rarely exceeds 4cm in diameter

Discrete, encapsulated mass which is sometimes nodular.

Pain is absent

HISTOLOGIC FEATURES

Large cells which have an eosinophilic cytoplasm and distinct cell membrane and which tend to be arranged in narrow rows or cords.

Oncocytes are arranged in sheets or nests and cords, which form alveolar pattern.

Some degree of cellular atypia, nuclear hyperchromatism and pleomorphism

Lymphoid tissue frequently present.

Cells are engorged with enlarged and morphologically altered mitochondria.

In recurrent tumors, there may be marked clear cell change and these tumors referred to as clear-cell oncocytoma.

TREATMENT

• Surgical

excision.

Sheet of eosinophilic oncocytes

Oncocytosis

• Oncocytic metaplasia is the transformation of ductal & acinar cells to oncocytes.

• Such cells are uncommon before the age of 50; as people get older, occasional oncocytes are common findings in the salivary glands.

• Oncocytosis refers to both the proliferation & accumumation of oncocytes within salivary gland tissue.

• It may mimic a tumor, both clinically & microscopically, but it is considered to be a metaplastic process rather than a neoplastic one.

Clinical features

• Found primarily in parotid gland.

• Most frequently in older adults (as with other oncocytic proliferations).

Histopathologic features

• Focal nodular collections of oncocytes within the salivary gland tissue.

• Enlarged cells are polyhedral & demonstrate abundant granular, eosinophilic cytoplasm as a result of the proliferation of mitochondria.

• Treatment

Discovered only as an incidental finding. No further treatment necessary.

Excellent prognosis.

Basal cell adenoma Clinical features

Occurs in the major salivary glands particularly parotid gland.

Minor glands – 2nd most common site, specifically the glands of the upper lip & buccal mucosa

Painless slow growth

2:1 male female ratio

Chiefly in adults with a peak prevalence in the seventh decade of life.

Appear as a firm swelling which may be cystic and compressible.

HISTOLOGIC FEATURES

Macroscopic -

A single well defined nodule.

Well defined capsule, whereas intraoral tumors are less well defined.

The cut surface is homogeneous with gray to brown in color.

MICROSCOPIC

Basal cells are uniform and regular.

Two morphologic forms seen:-

• One is a small cell with scanty cytoplasm and round deeply basophilic nucleus.

• The other cell is large with eosinophilic cytoplasm and an ovoid pale staining nucleus.

Four subtypes - solid, tubular, trabecular and membranous.

Solid type –

• Most common

• Basaloid cells form islands and cords that have a broad, rounded, lobular pattern.

Tubular type-multiple small, round duct-like structures

Trabecular type -

• Epithelial islands are narrower and cord like and are interconnected with one another, producing a reticular pattern.

Membranous type -

• Presence of abundant,thick, eosinophilic hyaline layer that surrounds and separates the epithelial islands.

• Epithelial islands are arranged in large lobules and appear to mold to the shape of other lobules to resemble a jigsaw puzzle pattern.

Treatment -

Excision

Basaloid cells arranged in a trabecular pattern

Membranous-

• Multilobular “jigsaw puzzle” pattern

• Thick eosinophilic hyaline layer.

Canalicular adenoma

Uncommon neoplasm composed of columnar epithelial cells arranged in a single or double layer forming branching cords in a loose stroma

Clinical features

Occurs in intraoral accessory salivary glands

Most commonly seen in the upper lip followed by palate, buccal mucosa, lower lip

Occurs in older adults with peak prevalence in 7th decade of life

Female predominance

Well circumscribed slowly growing, painless mass that usually ranges from several mm to 2cms.

Firm or somewhat fluctuant to palpation

Over lying mucosa is normal in color or bluish

Multifocal, with multiple separate tumors in the upper lip or buccal mucosa

Histologic Features

Single layered cords of columnar or cuboidal epithelial cells with basophilic nuclei

Cystic spaces enclosed by these cords & are usually filled with an eosinophilic coagulum

Loose fibrillar stroma with delicate vascularity.

Thin fibrous capsule.

Sometimes, rows of cells are closely approximated and appear as a double row of cells showing a “ party wall” appearance.

Treatment -

Enucleation or simple surgical excision

Uniform columnar

cells forming

canal like ductal

structures

FREQUENTLY ASKED QUESTIONS

Classify salivary gland tumours.

Short Notes on :

Histogenesis, Clinical features and histopathology of Pleomorphic Adenoma

Etiology, Clinical Features and histopathology of Warthin’s Tumour.

Objective Type:

Canalicular adenoma- Which is the most common site for its occurrence?

Histopathologic types of Basal cell adenoma.

What histopathologic pattern is seen in oncocytoma?

Name the histopathologic pattern seen in canalicular adenoma.

REFERENCES

• Text book of Oral Pathology. Shafer’s. Eighth edition.

• Oral & Maxillofacial Pathology. Neville. Third Edition.

• Clinical Pathologic correlations in Oral Pathology. Regezzi. Sixth Edition.

For any queries, mail to:

sharmaneepreeti@gmail.com