INTRODUCTION:
Necrotizing Sialometaplasia (NS) was first reported by Abrams et
al1 in the year 1973, who had added this new clinical
entity to the salivary gland pathology termed as “Necrotizing
Sialometaplasia” which was the histological description of the lesion -
as an inflammatory disease characterized by lobular necrosis by mucus
escape reaction and by marked squamous metaplasia and
pseudoepitheliomatous hyperplasia.This rare entity has been classified
under inflammatory and reactive lesions of salivary gland
diseases.2 This condition has been described as
non-neoplastic inflammatory condition of the salivary
glands2 and benign, self-limiting, reactive
inflammatory disorder of salivary tissue. NS can resemble a malignancy
and its misdiagnosis has resulted in unnecessary radical
surgery.3 Mesa et al had reviewed approximately 10,000
oral biopsy specimens in the year 1984 and had revealed only three cases
of necrotizing sialometaplasia, all of which had been misdiagnosed as
other benign entities, representing only 0.03 percent of biopsied oral
lesions.4 Shin et al. had reviewed all biopsy
materials taken from the oral cavity in a single institution in Korea
from 2012 to 2018 and found 4 cases of NS out of 726.5The largest series of cases of NS in the year 1991 reported average age
at the diagnosis as 45.9 years, Males outnumbered females by a ratio of
1.9: 1, and whites outnumbered blacks by a ratio of
4.9:1.6 It may arise in any area containing salivary
gland tissue. Classically, it involves the mucoserous glands of the hard
palate. Other sites where it has been reported include nasal cavity,
trachea, parotid gland, sublingual gland, submandibular gland, larynx,
buccal mucosa, maxillary sinus, tongue, tonsil, and retromolar
trigone.7 The etiology of this lesion is bizarre and
controversial. The most commonly proposed and generally accepted
etiology for NSM relates to ischemia.6 Other traumatic
injuries, such as dental injection, blunt force trauma, denture wear,
alcohol and tobacco use, as well as upper respiratory infections, have
been implicated as potential predisposing factors.7The exact pathophysiology of necrotizing sialometaplasia is unknown, but
ischemia of the vasculature supplying the salivary gland lobules is the
most widely accepted theory.8 furthermore, two
experimental studies were able to produce necrotizing sialometaplasia in
submandibular and sublingual glands of rats by ligating the vasculature
supplying these major salivary glands.9,10 This lesion
clinically presents as a deep ulcer, The size may range from 0.7 to 5.0
cm (average 1.8 cm) with sharply demarcated borders, often surrounded by
an erythematous halo. The posterior hard palate is the most common site
to be affected by NS and junction of the hard and soft palate being the
second most common site. About two-thirds of the palatal lesions are
unilateral; however, midline, bilateral synchronous and metachronus
lesions do occur.11,12 the diagnosis of this lesion is
based on the histological criteria proposed by Abrams et
al1., 1973 - The presence of ischemic lobular necrosis
of seromucous glands, squamous metaplasia of ducts and acini,
preservation of intact lobular architecture despite necrosis and
inflammation, and accumulation of necrotic de‐ bris in the adjacent
lobules.1 The diagnosis is mainly based on the
clinical features and histopathological analysis. Squamous cell
carcinoma and mucoepidermoid carcinoma has been considered as the
differential diagnosis in the previous literature. No specific treatment
is required since lesion is self-limiting and heals within the 6 to 8
weeks. This self-limiting condition has not yet been reported in Nepal
which led us to publish this rare entity.