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Necrotising Sialometaplasia
What is Necrotising Sialadenometaplasia /
Sialometaplasia?

Necrotising Sialadenometaplasia / Sialometaplasia is
an uncommon, usually self-limiting, variably ulcerated,
benign (i.e. non-cancerous), inflammatory process,
predominantly affecting salivary tissue (any site in the
body that contains elements of the salivary gland,
from the
para-nasal sinuses to the lung).

The importance of the lesion is that it
mimics the
appearance of malignant disease
, both clinically and
microscopically.  Failure to recognize
necrotising
sialometaplasia
may result in unnecessary radical
surgery because of an erroneous pre-operative
diagnosis of
squamous cell carcinoma or
muco-epidermoid carcinoma.
Photos of Necrotising Sialometaplasia in the Palate
(
Roof of Mouth)
What is the Cause of Necrotising Sialadenometaplasia /
Sialometaplasia?

Although the ætio-pathogenesis of necrotising
sialometaplasia
remains unknown there is general
consensus that a reduced blood flow (
ischæmic) event in
the
salivary gland precedes the development of the lesion.

This condition may occur after local trauma, including
surgical manipulation or injection of local anæsthesia into
the involved area.

For patients who have had surgery, the lesion becomes
clinically evident in about 3 weeks or longer.  
Necrotising
sialometaplasia
may also appear spontaneously, often
without the history of prior surgical or traumatic event.  No
particular oral condition or habit has been associated with
this condition to date.

The disease has been reported in patients with
vasculopathies which predispose to
ischæmia (such as
Sickle Cell Disease, where infarction may be a feature in
crisis,
Buerger’s disease and Raynaud’s phenomenon).

Addition of a
vaso-constrictor (such as adrenaline) to local
anæsthetic solutions, local radiotherapy, cocaine use,
pressure from local
space-occupying lesions and surgery
have also been implicated.  The lesion may be more florid
in pregnancy.

There is also an association with preceding
upper
respiratory tract infection
within the previous few weeks,
particularly acute on chronic
sinusitis and allergy.  It is
possible that the
ischæmic event in these cases is due to
immune complex disease, similar to the ætiology of
erythema multiforme or benign trigeminal sensory
neuropathy
.

It has been suggested that
necrotising sialometaplasia of
the
palate may represent an ulcerative or necrotising
stage of
smoker’s keratosis although this now seems
unlikely.

Other predisposing factors include:

  • intubation
  • bronchoscopy
  • local anæsthetic injection
  • vascular damage due to trauma
  • smoking and alcohol
  • hot food
  • fellatio and
  • recurrent vomiting

There may be an association with tumours, specifically:

  • Warthin’s tumour
  • Abrisokov’s tumour
  • carcinoma of the lip
  • rapidly growing mesenchymal malignancy and
  • salivary gland tumours.


What are the signs and symptoms of Sialadenometaplasia
/
Sialometaplasia?

Men are affected approximately twice as often as women.  
Mean age of occurrence in men is about 50 years and 36
years in women (the youngest reported case is 15 years).  
There appears to be an increased incidence in males.  
There was a 5:1 preponderance of Caucasians over Afro-
Caribbeans.

Necrotising sialometaplasia is extremely rare - there are
barely 200 cases reported in the world literature.

The vast majority (80%) of cases affect the
minor salivary
glands of the palate
, while other sites include gum behind
the lower wisdom teeth (
retro-molar pad), lip, tongue and
cheek.

The condition has also been reported in
major salivary
glands
.  Rarely, the condition has also been reported at
extra-salivary sites, which include:

  • nose
  • naso-pharynx
  • trachea
  • larynx and
  • lung.

At extra-salivary sites, the lesion may be described as
adenometaplasia.  A similar lesion occurs in the skin,
termed
syringometaplasia and similar histo-pathological
appearances have been described in the breast following
trauma.

The lesion has a sudden onset, and is clinically
characterized by a
nodular swelling that leads to a painful,
crater-like ulcer, 1 – 5 cm in diameter, with an irregular,
ragged border.  
The lesion mimics a carcinoma and is
usually located on the
posterior palate (most commonly at
the junction of the
hard and soft palates).

Symptoms are generally disproportionately slight,
compared with the size of the lesion.  Most patients
indicate surprisingly mild complaints of tenderness or dull
pain.  Pain may also be a feature at the onset and may be
intense and referral of the pain to the ear, eye and pharynx
are variable features which have been reported.  However,
development of the lesion may be painless and there are
even reports of anæsthesia of the
Greater Palatine Nerve
as the presenting feature.  This is thought to be caused by
involvement of the
vasa nervorum in the vasculitic
ætiological process.

The lesions may occur bilaterally and metachronously.

When ulceration occurs, it usually remains superficial, but a
single case of full-thickness
necrosis of the palate has
been reported.

Injection of anti-inflammatory
steroids into the lesions
appears to offer no benefit on recovery time of the lesion
or associated anæsthesia.

Differential diagnosis of an ulcer presenting with these
features could include:

  • direct traumatic ulceration
  • major aphthous ulceration
  • syphilis
  • tuberculosis
  • deep mycosis
  • agranulocytosis
  • neutropænia
  • nicorandil-induced oral ulceration
  • malignancy, in particular squamous cell carcinoma,
    low-grade muco-epidermoid carcinoma and oncocytic
    malignancies.


How is it treated?

The lesion usually heals spontaneously within 4 – 8 weeks.

The usual management of this condition is simple
observation until the healing phase is complete.

Necrotising sialometaplasia may occur de novo, after
trauma or a surgical procedure or in association with other
lesions, either benign or malignant.  Because of the latter,
whenever the diagnosis of
necrotising sialometaplasia is
made, close follow up is indicated until healing is
complete.  Recognition of the histological picture and the
varied clinical settings in which
necrotising sialometaplasia
can be found, is essential to avoid histo-pathological mis-
interpretation and inappropriate treatment for this benign
reactive condition.

The prognosis is excellent, once the correct diagnosis is
made.

There are no known preventative strategies.

If the lesions are large, incisional biopsy should be done to
establish a definitive diagnosis.

Healing takes place over several weeks by secondary
intention.  Reassuring the patient and lavaging the wound
with irrigation or rinsing may be helpful.  Once the lesion
has healed, recurrence and functional impairment are not
anticipated.


Useful Website:

European Association of Oral Medicine


Useful Articles:

J American Dental Association 1996. Necrotizing
sialometaplasia: literature review and case reports.

Ear, Nose & Throat Journal 2003.  Necrotizing
Sialometaplasia.

Oral Oncology 2006. Case Report. Necrotizing
sialometaplasia of the palate.

J Canadian Dental Association 2007.  Sialometaplasia of
the Soft Palate in a 2-Year-Old Girl.

Cases Journal 2009.  Case report.  Bilateral localization of
necrotizing sialometaplasia.  A case report.
Last Updated 22nd November 2010