Salivary glands

Inflammatory

Necrotizing sialometaplasia


Editorial Board Member: Marc Pusztaszeri, M.D.
Deputy Editor-in-Chief: Kelly Magliocca, D.D.S., M.P.H.
Molly Housley Smith, D.M.D.

Last author update: 21 February 2024
Last staff update: 21 February 2024

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PubMed Search: Necrotizing sialometaplasia salivary glands

Molly Housley Smith, D.M.D.
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Cite this page: Smith MH. Necrotizing sialometaplasia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/salivaryglandsnecrotizingsialo.html. Accessed April 14th, 2024.
Definition / general
  • Reactive, self resolving inflammatory condition of the salivary glands that most often affects the palate and is known to mimic malignancy both clinically and histopathologically
Essential features
  • Classically begins as a swelling that evolves into a crater-like ulceration, which resolves within 3 - 12 weeks
  • Most commonly affects the palate
  • Necrosis or disruption of salivary acini with squamous metaplasia of ductal structures
  • Etiology is thought to be a reaction to trauma or smoking in a setting of vascular compromise / tissue ischemia
  • Mimics malignancy both clinically and histopathologically
Terminology
  • Not recommended: adenometaplasia
ICD coding
  • ICD-10: K11.8 - other diseases of salivary glands
  • ICD-11: DA04 - diseases of salivary glands
Epidemiology
Sites
  • Hard palate is the most common site
  • Other sites include buccal mucosa, floor of mouth, nasal cavity, trachea, parotid gland, sublingual gland, submandibular gland, larynx, maxillary sinus, tongue, tonsil and retromolar trigone (Arch Pathol Lab Med 2009;133:692)
Pathophysiology
  • Unknown pathogenesis; thought to be caused by vascular ischemia that interrupts the blood supply to the underlying salivary glands (Stomatologija 2022;24:56)
Etiology
Clinical features
Diagnosis
Radiology description
Radiology images

Images hosted on other servers:
Rare bony erosion

Rare bony erosion

Prognostic factors
Case reports
Treatment
Clinical images

Contributed by Douglas Damm, D.D.S., Ashley Clark, D.D.S.,
Eric Mencarelli, M.D., D.D.S. and Molly Housley Smith, D.M.D.

Palatal ulceration and erythema

Palatal ulceration and erythema

Midline palatal ulceration

Midline palatal ulceration

Bilateral palatal ulcerations Bilateral palatal ulcerations

Bilateral palatal ulcerations

Microscopic (histologic) description
  • Squamous metaplasia of ductal structures and acini with preservation of the salivary lobular architecture is an essential feature, according to World Health Organization (see WHO classification-oral cavity & oropharynx)
  • Necrosis / infarction of acini characterized by loss of nuclei and cell borders with or without zones of spilled mucin
  • Pseudoepitheliomatous hyperplasia with generally bland cytology or keratinocytic regenerative atypia
  • Reactive, myxocollagenous background stroma
  • Surface ulceration, granulation tissue and subacute inflammation may be present
  • Has been conceptualized by 5 histologic stages of development and evolution: infarction, sequestration, ulceration, repair and healing (Int J Oral Surg 1982;11:283)
Microscopic (histologic) images

Contributed by Kelly Magliocca, D.D.S., M.P.H. (Case #497) and Molly Housley Smith, D.M.D.
Missing Image Missing Image

Metaplasia of residual salivary ducts

Pseudoepitheliomatous hyperplasia

Pseudoepitheliomatous
hyperplasia

Bland cytology

Bland cytology

Spilled mucin

Spilled mucin


Surface ulceration

Surface ulceration

Glandular necrosis

Glandular necrosis

Acute inflammation

Acute inflammation

Healing stage

Healing stage

Positive stains
Sample pathology report
  • Hard palate, incisional biopsy:
    • Necrotizing sialometaplasia (see comment)
    • Comment: The microscopic sections show ulcerated mucosa with zones of pseudoepitheliomatous hyperplasia without prominent cytologic atypia. Squamous metaplasia of ductal structures with preservation of lobular architecture is appreciated along with necrosis of salivary acini and extravasated mucin. No evidence of a neoplasm is identified upon review of multiple deeper levels. Clinical follow up to ensure complete resolution of the lesional tissue is recommended.
Differential diagnosis
  • Although the clinical differential diagnosis for an ulceration or swelling on the palate may include a variety of entities (e.g., salivary gland neoplasm, T cell lymphoma, granulomatosis with polyangiitis, deep fungal or bacterial infection), the main histopathological differential diagnosis includes mucoepidermoid carcinoma, squamous cell carcinoma or subacute necrotizing sialadenitis
  • Mucoepidermoid carcinoma (MEC):
    • Can be challenging to differentiate NSM from MEC on fragmented biopsies or in the later stages of NSM (Head Neck Pathol 2022;16:54)
    • Lobular architecture is not preserved
    • S100 negative
    • Depending on the grade of MEC, the following features may be seen in MEC but not in NSM (Arch Pathol Lab Med 2009;133:692)
      • Cystic spaces
      • Cellular pleomorphism / atypical mitotic figures
      • Presence of perineural / lymphovascular invasion
      • Proliferation of apparently neoplastic goblet cells
      • Lack of intact lobular architecture
    • May show t(11;19)(q14-21;p12-13) with CRTC1(MECT1)::MAML2 fusion
  • Squamous cell carcinoma (SCCa):
  • Subacute necrotizing sialadenitis (SNS):
Board review style question #1

Necrotizing sialometaplasia most commonly affects what site?

  1. Minor salivary glands of the lip
  2. Minor salivary glands of the palate
  3. Parotid
  4. Submandibular gland
Board review style answer #1
B. Minor salivary glands of the palate. Although necrotizing sialometaplasia can affect any of the given answer choices, it classically involves the minor salivary glands of the hard palate. Answers A, C and D are incorrect because necrotizing sialometaplasia occurs at these sites less frequently than in the minor salivary glands of the palate.

Comment Here

Reference: Necrotizing sialometaplasia
Board review style question #2

A patient presents to clinic with severe pain and an ulceration on the hard palate. She states that the lesion began after a dental procedure as a swelling that rapidly progressed to an ulceration over the course of a couple weeks. What is the diagnosis?

  1. Mucoepidermoid carcinoma
  2. Necrotizing sialometaplasia
  3. Squamous cell carcinoma
  4. T cell lymphoma
Board review style answer #2
B. Necrotizing sialometaplasia. The patient presented with the classic clinical history of acute onset of a rapidly progressing lesion on the hard palate, which began as a swelling that subsequently ulcerated. Biopsy revealed large zones of pseudoepitheliomatous hyperplasia, squamous metaplasia of ducts, lack of overt pleomorphism and areas of acinar necrosis and mucin spillage. Answer A (mucoepidermoid carcinoma) is incorrect because the lobular architecture of the gland is preserved and there is no proliferation of cystic spaces or neoplastic goblet cells. Although T cell lymphomas classically may affect the hard palate, answer D is incorrect because the biopsy did not show an atypical lymphoid infiltrate. Answer C (squamous cell carcinoma) is incorrect as the proliferation of squamous epithelium classically forms the pseudoepitheliomatous hyperplasia type pattern and lacks cellular pleomorphism.

Comment Here

Reference: Necrotizing sialometaplasia
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