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This uncommon condition is usually diagnosed by the pathologist and accounts for 0.03% of all biopsy diagnoses of the oral cavity. It is more common in males with a male:female ratio of 1.5-2:1 and usually occurs in patients > 40 years old. It most commonly presents with a painful lesion of the hard palate, usually with ulceration. It is a self-limited condition and no treatment except for symptomatic relief is needed. It probably results from ischemic changes involving the minor salivary glands and thus can be found in the nasal cavity, gingiva, lip, hypopharynx, maxillary sinus, and major salivary glands. There is a primary form which usually involves the minor salivary glands of the palate and is of unknown etiology.

Under the microscope, the key microscope features are the lobular necrosis of the salivary gland tissue, preservation of the lobular architecture, squamous metaplasia of the residual ducts and acini, and temporal variability of the inflammatory cell infiltrate.

The importance in making this diagnosis rests with the pathologist distinguishing this disorder from a malignancy. The table below illustrates helpful features to make this distinction. The key point for the pathologist is a diagnosis of a squamous cell carcinoma or mucoepidermoid carcinoma of the palate should never be made until necrotizing sialometaplasia is excluded.

Differential Diagnosis of Atypical Squamous Proliferations Within the Oral Cavity

Histology Necrotizing Sialometaplasia Mucoepidermoid Carcinoma, Low Grade Squamous Cell Carcinoma
Architecture/growth Retention of lobular architecture Haphazard, infiltrative growth Haphazard, infiltrative growth
Cellular components Smooth, round to oval nests of metaplastic squamous epithelium with bland cytology
Residual ductal lumina with mucous cells
Admixture of mucous, intermediate,and epidermoid cells
Bland cytology
Irregular cell nests
Nests and cords of squamous cells with irregular outlines and variable amounts of cytologic atypia
No mucin within tumor
Cyst formation Absent Present and prominent Absent
Surface epithelium May show pseudoepitheliomatous hyperplasia, usually not connected to main lesion Uninvolved
Not connected with tumor
Often dysplastic and/or in direct continuity with the carcinoma
May ulcerate
Extravasated mucin necrosis May be present
Lobular infarction of salivary gland acini
Absent May show tumor necrosis
Inflammation May be prominent May be prominent with mucin extravasation

May be present
Association desmoplasia

Am J Clin Pathol 1977;67:315-317.
Pathol Case Rev 2000;5:221-226.

Commonly Used Terms

Mouth and Oral Cavity

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Last Updated 4/1/2001

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