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.