Salivary
neoplasms (Table 42.5)
The
investigation of salivary neoplasms
For parotid and submandibular tumours CT and MRI scanning are the most
helpful imaging techniques (Figs 42.10 and 42.11). They will confirm that the
mass being investigated is indeed intrinsic to the gland, they accurately image
the borders of the tumour and show whether it is well circumscribed and benign
or diffuse, invasive and malignant. In addition they show the relationship of
the tumour to other anatomic structures and help with the planning of subsequent
surgery.
Open
surgical biopsy of intrinsic neoplasms of the major glands is absolutely
contraindicated. At least 75 per cent of all parotid tumours and more than 50
per cent of all submandibular gland tumours will prove to be benign pleomorphic
adenomas. This tumour which is only poorly encapsulated is very tense and if an
incision is made into it the contents of the tumour burst into the surrounding
tissue planes and it is impossible to eradicate the microscopic
Fine
needle aspiration (FNA) biopsy is a safe alternative to open biopsy of a major
gland. Evidence suggests that provided the needle gauge does not exceed 18 G
there is no risk of seeding viable tumour cells. Although advocates of this technique
claim high accuracy and specificity, there is inevitably a high risk of sampling
error.
Epithelial
tumours
Seventy-five per cent of all salivary epithelial tumours arise in the
parotid glands and, of these, only 15 per cent are malignant. Just over 10 per
cent occur in the submandibular glands and, of these, approximately one-third
are malignant. About 15 per cent of tumours occur in the minor salivary glands
and nearly half of these will be malignant. Tumours arising in the sublingual
glands are rare (0.3 per cent) but nearly all of them will be malignant.
— carcinomas — occur.
Of the variety of benign adenomas that has been described only two —
the pleomorphic adenoma and Warthin’s tumour
The
pleomorphic adenoma occurs at any age (mean 42 years) and has an equal sex
incidence. It accounts for at least 75 per cent of parotid tumours and more than
50 per cent of submandibular tumours. It accounts for rather less than 50 per
cent of minor gland tumours. Clinically the tumour has the texture of cartilage
and has an irregular and bosselated surface. In the palate, the overlying mucosa
is rarely ulcerated. Very rarely after a number of years the tumour may undergo
malignant change and for this reason all patients presenting with pleomorphic
adenomas should be advised to undergo surgical removal of the tumour (Fig.
42.12).
The
Warthin’s tumour occurs only in the parotid gland where it accounts for
approximately 15 per cent of all neoplasms. It is a disease of the elderly with
a mean age of presentation of 60 years. Historically it had a male:female ratio
of 4:1 but it is now becoming increasingly common in females. Recent evidence
suggests that this tumour is related to cigarette smoking. It is also unusual in
that in
10 per cent of cases it arises either bilaterally or is multicentric in
the one gland. It does not undergo malignant change.
Carcinomas
The acinic cell carcinoma and the mucoepidermoid carcinoma, although
undoubtedly malignant tumours with a potential for local invasion and metastatic
spread, are frequently very low grade histologically and do not require the
radical treatment needed for more aggressive tumours. Together they account for
only 5 per cent of all tumours at any sire. The mucoepidermoid tumour is
much more common in the USA where it forms 10 per cent of all salivary
neoplasms.
The
adenoid cystic carcinoma, adenocarcinoma, squamous cell carcinoma and
undifferentiated carcinoma are all aggressive malignant tumours that carry a
poor prognosis regardless of treatment. The adenoid cystic carcinoma is characterised
by relentless perineural spread along the cranial nerves and into
the brain. However, it grows extremely slowly and
Management
of epithelial tumours
Both benign and malignant tumours arising in the parotid or
submandibular glands are treated surgically by excision with surgical clearance.
In the parotid gland this is by either superficial or total parotidectomy according to the location of the tumour. Unless the patient presents with facial
nerve palsy (indicating a malignant tumour) the facial nerve is always
preserved. In the submandibular gland treatment is always by excision of the
gland. If when a definitive pathological diagnosis is received the tumour is
malignant then the patient should receive radical postoperative radiotherapy. In
those cases when the tumour involves skin or other adjacent structures or where
there is lymphatic metastasis the patient should undergo radical excision,
including a neck dissection and sacrificing any structures invaded by tumour,
and again treated with postoperative radiotherapy.
Pleomorphic
adenomas arising in the minor salivary glands can be treated by local excision
with a 5-mm margin. They do not invade periosteum and so in the palate they
should be excised subperiosteally. Mucoepidermoid carcinomas and acinic cell
carcinomas require rather more radical excision with a 10-mm margin and, when
they are situated in the palate, palatal fenestration should be undertaken.
Postoperative radiotherapy is only indicated for high-grade tumours or if the
margins are not clear. For the remaining carcinomas arising in the minor
salivary glands radical surgical excision and postoperative radiotherapy are
indicated. In the palate this will be by maxillectomy.
Nonepithelial
tumours
A variety of nonepithelial tumours can arise in the salivary glands.
Haemangiomas and lymphangiomas (cystic hygromas) occur in childhood.
Haemangiomas occur mostly in the parotid and appear shortly after birth and grow
progressively for several months. The majority undergoes spontaneous regression
by 2 years of age. Females are more frequently affected. Lymphangiomas are less
common. They may affect any of the salivary glands. They form sponge-like
multicystic lesions. Fifty per cent are manifest by 12 months and 90 per cent
will be evident by the end of the second year. They do not undergo spontaneous
involution. They frequently extend into the neck and mediastinum, and can
undergo dramatically rapid growth causing respiratory obstruction. Treatment
is by complete surgical excision but this may be technically very difficult.
Neurofibromas
and neurilemmomas are the commonest nonepithelial tumours arising in adults.
Clinically they are
nor distinguishable from other salivary tumours and are only diagnosed
following surgery for a presumed epithelial tumour. Lipomas occur in the parotids
particularly in adult males. They are treated by surgical excision.
Malignant
lymphomas
True extranodal lyrnphoma arising in the salivary glands —usually the
parotids — is rare. More common is lymphoma arising from the lymph nodes
either on the surface of the glands or within the parenchyma of the gland.
Lymphoma also arises in the salivary glands, as a complication of HIV disease,
and also in benign lymphoepithelial lesion and Sjogren’s syndrome. The peak
incidence for nonHodgkin’s lymphoma is the sixth and seventh decades and
females are twice as likely as males to be affected.
Salivary
gland lymphomas usually present as firm painless swellings and more than 90 per
cent occur in the parotids. If the lymphoma is confined to the parotid,
treatment is by parotidectomy with postoperative radiotherapy. If there is
evidence of spread beyond the salivary gland, treatment is by polychemotherapy according to the accepted protocols based on histological characterisation.
Unclassified
and allied conditions
Sialosis is an uncommon noninflammatory cause of salivary swelling
usually affecting the parotid glands symmetrically. It is usually associated
with metabolic and endocrine conditions such as alcohol abuse, diabetes
mellitus, pregnancy, malnutrition and some drugs (usually sympathomimetics). It
usually affects middle aged and elderly adults who present with bilateral soft parotid
swellings. Biopsy of the glands reveals extensive fatty replacement but
otherwise normal tissues. No treatment is known to be effective but sometimes
parotidectomy is required to correct the disfigurement.
Necrotising
sialometaplasia, benign lymphoepithelial lesion, salivary duct cysts, Kuttner tumour
and cystic lymphoid hyperplasia of HIV disease can all mimic salivary
gland neoplasia. Similarly, branchial cysts and dermoids can present diagnostic
confusion on occasion. As has already been discussed both sarcoid and
toxoplasmosis can present as parotid pseudotumours.