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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.
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