Necrotizing sialometaplasia is a rare, benign inflammatory disease of the minor mucous salivary glands usually caused by glandular ischemia or trauma, that can mimic malignancy, but has a self-limiting character. Physicians should be aware of its clinical and histological traits in order to avoid unnecessary disfiguring surgery.
Necrotizing sialometaplasia usually presents suddenly and can be precipitated by trauma, vomiting , surgery  or radiation therapy. Cases may also occur in patients with neoplasia or chronic inflammatory diseases and have also been reported after mucocele excision .
Physical examination reveals the pathological process as an inflammation and swelling of a minor salivary gland located in the hard palate area  that can also take the form of an ulcer, usually with a diameter of 0.7 to 5 cm . Lesions may also be bilateral  or located in other regions of the oral cavity like incisive canal, maxillary sinus, parotid glands , tongue , nasal cavity , larynx  or other sites in the upper respiratory tract , including the trachea , but usually involve the palatal midline . Necrotizing sialometaplasia of the breast , skin (in this case being termed syringometaplasia ) and lungs  have also been published. Palatal bone erosion may occur with both ulcerated and non-ulcerated lesions, making it difficult to distinguish from malignant tumors. Wegener granulomatosis, abscesses, and extranodal lymphoma must also be excluded, and this is only possible after performing a biopsy. With prolonged evolution, spontaneous healing is usually observed .
The lesions are accompanied by general symptoms, such as malaise, fever, and chills and may be painful or can be associated with a loss of sensations over the mucosa of the palate . They occur more often in men in the fourth decade of life .
Entire Body System
Jaw & Teeth
- Parotid Mass
We report a case of necrotizing sialometaplasia diagnosed after superficial parotidectomy due to bilateral parotid masses in a 69-year old heavy smoking female. [ncbi.nlm.nih.gov]
On examination the parotid mass was firm and mildly tender. A clinical diagnosis of parotid tumor was kept and a fine needle aspiration cytology (FNAC) was conducted. [ccij-online.org]
- Parotid Swelling
We present a case of a parotid swelling that appeared as Warthin tumor on fine needle aspiration cytology (FNAC). On histology it turned out to be NS of parotid gland. [ccij-online.org]
These findings suggest that vascular occlusion by the neoplastic cells produces ischemia, which leads to local infarction contributing to the salivary gland lesion. [ncbi.nlm.nih.gov]
Suomalainen et al 12 suggested that the degree of the inflammatory reaction can be reflected in the above stages of NS. [doi.org]
Face, Head & Neck
A radiography of the affected area is needed in the presence of palatal bone erosion  , but the definite diagnosis depends on histological examination of a biopsy specimen which must be taken from the base and margin of the ulcer and should be large and deep enough to ensure proper analysis, in order not to erroneously diagnose pseudoepitheliomatous mucous hyperplasia, mucoepidermoid carcinoma or squamous cell carcinoma. Microscopic examination reveals squamous ductal metaplasia and necrosis of the minor salivary glands. An inflammatory infiltrate composed of neutrophils, macrophages, eosinophils, plasma cells and lymphocytes (mixed inflammatory reaction), as well as mucin extravasation  and necrotizing sialadenitis are also present. Lobular architecture is not disrupted.
If the diagnosis remains uncertain, immunohistochemistry study is indicated. This evaluation will show no p53 immunoreactivity, low MIB1 (Ki-67) immunoreactivity and the presence of 4A4/p63 and calponin-positive myoepithelial cells. Other markers that may prove useful are smooth muscle antibody and p63. Basement membrane markers like E-cadherin, type IV laminin, and various cytokeratins (CK5, CAM 5.2, CK6, CK7,) can also be used  . Hematoxylin-eosin staining should also be performed . Depending on the time when a biopsy is obtained, the patient could be in one of the following stages: infarction, sequestration, ulceration, repair or healing . Epithelial atypia may also be present. These may coexist in different areas of the lesion and their extent depends on the healing ability of the patient.
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