TUMORS OF SALIVARY GLANDS
-neoplasms of salivary gland are uncommon, comprise only about 3 % of all
tumors of the head and neck
-about 85 % occur in major salivary glands, of these 90% in parotid, 19%
in submandibular gland, less than 1% involves sublingual gland
-of the 15% that occur in minor salivary gland, most commonly these
tumors arise fom the palate
-although the tumors of minor gland are less common, half of them are
malignant (compared to 15% of malignant tumors in parotid gland)
-salivary gland are difficult to classify because of wide variety of
histological appearances and variability in clinical behavior that is often difficult
to predict
according to last issue of WHO classification (2005):
1. Malignant epithelial tumors
2. Benign epithelial tumors
3. Soft tissue tumors
4. Hematolymphoid tumors
5. Secondary (metastatic) tumors
1) MALIGNANT EPITHELIAL TUMORS
1- Acinic cell carcinoma
-Acinic cell carcinoma constitutes about 18% of all malignant salivary gland
tumors.
-majority of AciCCs (80-90%) arise in the parotid gland, followed by minor
salivary glands, especially of the oral cavity, and submandibular gland. Women
are affected slightly more often.
-AciCC occurs over a wide age range with peak incidence in the 4th to 5th
decades.
-AciCC is the second most common malignant salivary gland tumor in
childhood after mucoepidermoid carcinoma.
-Familial occurrence of AciCC of the parotid gland has been described
clinically: slow-growing, painless swelling, some tumor behave in more aggressive
fashion, with rapid growth
-typical clinical presentation is that of slowly growing painless mass and it
often mimics benign tumor
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-Duration of clinical symptoms is variable with range from several month
to 40 yrs. Facial nerve involvement is found in up to 10% of cases
histologically: composed of the cells with a similarity with acinar serous
cells (secretory granules in the cytoplasm) arranged in solid and microcystic
patterns, in some cases-there is abundant lymhocytic infiltration in the stromaexcellent prognosis
prognosis and treatment: about 20% of tumors develop recurrent tumor, 10%
give rise to metastases, distant metastases are rare
-long follow-up period is necessary- meta can develop many years after
surgical removal of the primary tumor
2- Mucoepidermoid carcinoma
-mucoepidermoid carcinomas is one of the most common malignant salivary
gland tumors, especially frequent in minor glands
-may occur at any age, but most often seen in middle adult age (5-6th
decades), most common malignant tumor of SG in children
-all mucoepidermoid carcinomas have malignant potential but most present
clinically as slowly growing painless masses, 10 per cent develop distant
metastases, five-year survival is 90%
histologically: composed of squamous cells, mucus-producing cells and the cells of
intermediate type
-well-differentiated tumor- low-grade carcinoma- is predominantly cystic,
consists od mucus producing cells, is well circumscribed- better prognosis
-poorly differentiated- high-grade type- is solid, composed predominantly of
intermediate and squamous cells- poorer prognosis- five-year survival only 25%distant metastases are seen in one-third of patients
3- Adenoid cystic carcinoma
-is a distinctive salivary gland malignant tumor characterized by
aggressive clinical behaviour, pain- propensity to perineural invasion
-this is one of the most common malignant salivary gland tumorscomprises 5-10% of major salivary gland tumors and 15-30% of minor salivary
gland tumors
-intraorally- most frequent site is the palate, usually presents in middle
age, can cause pain, often present as ulceration of oral mucosa
-histologically: composed of three growth patterns- cribriform, tubular
and solid, cytologically constits of two types of tumor cells- epithelial and
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modified myoepithelial- histological hallmark is a formation of pseudocystsextracellular spaces containing proteoglycans and basement membrane material
-adenoid cyst carcinoma is malignant tumor which infiltrates, invades local
tissue including the bone, and often causes metastases and recurrences,
perineural and perivascular spread is very characteristic
-late blood-born metastases present in half of cases- lungs, bone, liver,
brain-lymph node involvement is less common
prognosis: five-year survival is 70%, but survival drops to 30% after 15 yearslong course of disease is typical
4- Polymorphous low-grade adenocarcinoma
-low-grade malignancy, it involves minor glands of oral cavity
-it consists of cytologically bland uniform cells- arranged in a variety of
heterogenous growth patterns- such as glandular, solid, trabecular, fascicular,
tubular, cribriform tec
-invasive growth pattern without capsule, perineural invasion is common
prognosis: excellent, recurrences in minority of cases, no metastases
5-Epithelial-myoepithelial carcinoma
-malignant salivary gland tumor composed of two cells types, they form bilayered
ductal structures composed of outer layer of clear myoepithelial cells and inner
layer of luminal ductal cells
-prevalent in women, peak age 6th to 7th decades, most commonly in
parotid gland, metastatic sites include lung, lymph nodes, liver
-clinically- low grade malignancy, recurrences in 40%, metastases in 15 %
6- Basal cell adenocarcinoma
malignant tumor composed of basaloid cell with infiltrative growth pattern and
potential for recurrences and metastases
-over 90% occur in parotid gland, age about 60 yrs
-patients with basal cell carcinoma may have multiple adnexal skin tumors
(Brooks-Spiegler disease) associated with mutation in CYLD gene
7- Cystadenocarcinoma
-rare malignant tumor characterized by predominantly cystic growth pattern,
mostly it exhibits intraluminal papillary growth
-produces mucin
-slowly growing malignancies- low grade
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8- Salivary duct carcinoma
-agressive type of salivary gland carcinoma that resembles histologically ductal
invasive breast cancer
histologically composed of large polymorphic cells with eosinophilic cytoplasm,
many mitotic figures, solid areas show focal necrosis (so called comedo-like
necrosis), perineural and vascular invasion is common
prognosis: poor- the tumor is very agressive, it grows and spreads rapidly,
common metastases to lymph nodes
9- Adenocarcinoma
-common tumor, it has glandular ductal differentiation, it occurs both in major
and minor glands, in most cases low grade
10- Myoepithelial carcinoma
-malignant salivary gland tumor composed predominantly of myoepithelial cells,
characterized by invasive growth pattern and potential for metastases
most cases arise in parotid, may develop in pre-existing PA
-histology- multinodular growth pattern-composed of spindle shaped cells,
epithelioid and clear cell with immunophenotype of modified myoepithelial cells
-clinically- destructive locally aggressive, prognosis- 1/3 cured by surgery, 1/3
die of disease, 1/3 survive with recurrent and meta disease
11-Carcinoma in pleomorphic adenoma
-development of secondary carcinoma in pre-existing pleomorphic adenomaoccurs in about 5 % to 10% of PA- frequency is time related
prognosis: poor, high grade malignancy- metastatic disease
histology: salivary duct carcinoma, adenocarcinoma, undifferentiated carcinoma,
myoepithelial carcinoma (in descending order)
12- Carcinosarcoma
-can be regarded a variant of malignancy arising in pleomorphic adenoma, in
which both epithelial and stromal components become malignant
-epithelial component represents adenocarcinoma or undifferentiated ca,
stromal component is mostly chondrosarcoma, poor prognosis
13- Squamous cell carcinoma
-primary -very rare in salivary glands, in majority of cases- squamous cell
carcinoma represents an intraparotideal intraglandular metastasis- from primary
tumor in head and neck region, such as squamous cell carcinoma or melanoma of
the skin
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14- Lymphoepithelial carcinoma
-uncommon malignant tumor of salivary gland, comprising less than 1%
-it shows striking racial predilection for Inuits (Eskimo) in the arctic regionsnear 100% association with EBV- in endemic regions-serologic studies show
elevated titres of anti-EBV viral capsid antigen, in non-endemic ares- EBV usually
absent
-80% parotid, followed by submandibular gland
-morphologically indistinguishable from nasopharyngeal ca
-clinical presentation- slowly growing mass, propensity to develop local lymph
node meta, distant meta in about 20% (lung, liver, bone, brain)
15- Sialoblastoma
-rare potentially aggressive tumor of parotid or submandibular gland, usually
present at birth or shortly after
-about 10% metastasize
2) BENIGN EPITHELIAL TUMORS- benign tumors are more common then
malignant
1- pleomorphic adenoma- most common salivary gland tumor, it accounts
for over 50% of all SG tumors, most common in middle age- 4.-6.decade
-mainly seen in parotid gland, in the superficial lobe, but occurs also in
submandibular gland and in the oral cavity - site of predilection is at the junction
of hard and soft palate
grossly: well-circumscribed, but encapsulation is incomplete- there is often a
compressed fibrous tissue around the tumor, but it is variable in thickness and
may be absent in places
-firm, solid consistency
histologically: the tumor shows a variety of appearances, both in different
areas of a single tumor and between tumors
-the neoplasm consists of solid sheets and masses of polygonal cells, of
the duct containing mucus, of the interlacing strands and cords of epithelial and
myoepithelial cells and of spindle-shaped cells that appear to blend into the
background stroma
-the stromal changes are characteristic-there may be normal fibrous
tissue in the stroma, but more often this becomes hyalinized, mucoid, myxoid
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and chondroid with resemblance to hyaline cartilage- there may be osseous and
adipose metaplasia in the tumor
-these extracellular matrix deposits seem to be a product of secretory
activity of modified myoepithelial cells
clinically: benign, but a significant risk of recurrences- up to 50 %
- tendency for pleomorphic adenoma to recur is mainly related to the morphology
and surgical management- focal lack of capsule, tumor tends to invade the
capsule, and may bulge through it while remaining attached to the main tumor
mass by a small istmus- it is easy to leave these bulging pieces of tumor in situ
during local excision, superficial or total parotidectomy is recommended instead
of enucleation (simple excision)
- pleomorphic adenoma may undergo malignant transformation to carcinoma rate is variable- lies between 5 to 10 % (risk increases with duration)- carcinoma
ex pleomorphic adenoma has very poor prognosis
2-Myoepithelioma
-rare benign salivary gland tumor composed entirely of neoplastic
myoepithelial cells
-uncommon, accounts for less than 1 % of all salivary gland tumors
grossly: well circumscribed, may arise both in major glands and in minor glandsusually encapsulated3-Basal cell adenoma
benign epithelial tumor of salivary gland origin, most common in parotid
grossly- well circumscribed, encapsulated
microscopically: the tumor is composed of uniform regular islands or cords
of neoplastic epithelial cells with peripheral palisading
4- Warthin's tumor = adenolymphoma
-occurs only in parotid gland, more common in old people, age peak: 6.-8. decade
may be multicentric and bilateral
histologically: the tumor has very characteristic appearance resulting from two
main components-epithelial oncocytic arranged in cystic papillary structures and
lymphoid stroma
- the epithelium forms cysts with papillary processes extending into them,
cystic spaces are lined by bilayered epithelium with oncocytic change -abundant
eosinophilic granular cytoplasm (filled with abnormal mitochondria)
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- the stroma contains a variable amount of lymphoid tissue with welldifferentiated germinal centres of follicles
clinically: the tumor is benign, without recurrences-new data show polyclonal
nature, malignant transformation is exceptional-carcinoma or lymphoma can
develop
5- Oncocytoma
-rare, benign, well-circumscribed tumor, can be multifocal and bilater
histologically: -composed of large epithelial cells with eosinophilic granular
cytoplasm (oncocytes)
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cytoplasm of oncocytes is filled with enlarged and structurally abnormal
mitochondria
6- Cystadenoma
-benign SG tumor characterized by predominantly multicystic growth pattern,
the epithelial lining is papillary, oncocytic, mucinous, squamous, apocrine, etc.
-can occur both in major and minor glands, in adults- 45% in parotid gland
MESENCHYMAL TUMORS
Vascular tumors are the most common benign mesenchymal tuHemangioma- greatest occurrence in 1st decade, it
proliferation of endothelial cells, almost exclusively in parotid gland
represents
Clinical features- most appear during the first 6 months- slowly growing masses,
neonatal and infantile lesions may grow rapidly
Lipoadenoma- benign neoplasm composed of mixture of mature adipose
tissue and glands, slowly growing
Neurofibroma- arises in facial nerve, parotid gland involved
HEMATOLYMPHOID TUMORS
-primary SG lymphomas are uncommon-accounting for 5% of all extranodal NHL.
Extranodal marginal zone B-cell lymhoma (MALT lymphoma)- the most
common, associated with LESA- is a low grade neoplasm
-patients with Sjogren sy- develop BLEL (benign lymphoepithelial lesion)
-prognosis is favourable-tumors are localized to parotid gland, rare cases may
disseminate to cervical LN and/or transform to high grade NHL
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diffuse large B-cell lymphoma (DLBCL)- composed of large B cells, the
tumor is infiltrative
extramedullary plasmocytoma- soft tissue malignant tumor composed of
monoclonal plasma cell proliferation, no association with multiple myeloma
-involvement of SG is rare, old patients (6th to 7th decade), favourable
outcome- excision is curative
SECONDARY TUMORS
-comprise about 5% of all malignant SG tumors, majority of metastatic tumors
located in parotid gland
-meta can occur within the gland directly or in lymph nodes (intraglandular and
periglandular)
-primary tumors: Most arise in head and neck area (80%)-facial skin malignant
melanoma, squamous cell carcinoma of the skin, oral cancer
-less commonly –distant primary tumors (small cell ca of lung, kidney and breast
carcinomas)
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