Necrotizing sialometaplasia. (Pathology Clinic).

Necrotizing sialometaplasia is a benign, self-limited, reactive inflammatory process that involves salivary glands. It occurs in middle-aged patients; men are affected slightly more often than women. Patients may experience an antecedent event (e.g., surgery, radiation, or trauma) up to 3 weeks before necrotizing sialometaplasia appears clinically, but many are asymptomatic. A submucosal nodular swelling will give way to an ulcerative, crater-like lesion that usually measures less than 3 cm in its greatest dimension.

Necrotizing sialometaplasia most commonly arises in the minor salivary glands of the hard palate; other mucosal sites are affected less frequently. The histologic marker of necrotizing sialometaplasia is preservation of the smooth contour and lobular architecture of the salivary glands following coagulative necrosis and subsequent ductal and acinar squamous metaplasia (figure 1). The metaplastic squamous epithelium has a bland overall histologic appearance (figure 2). However, as is the case with any reparative or regenerative epithelium, enlarged nuclei, prominent nucleoli, apoptosis, and mitotic figures can be seen (figure 3). Inflammatory cells, including neutrophils and lymphocytes, are often prominent in the surrounding tissues. In an attempt at re-epithelialization, necrotizing sialometaplasia may induce pseudoepitheliomatous hyperplasia, and this reaction may be so strilting that distinguishing it from squamous cell carcinoma and mucoepidermoid carcinoma may be difficult. The difficulty is compounded w hen the biopsy specimen is small and features a predominance of fibrosis and inflammatory elements. The lobular architecture, the overall smooth edges of the epithelial islands, the uninvolved salivary glands, and the limited degree of cytologic atypia can help differentiate these diseases. Often the self-limiting nature of necrotizing sialometaplasia helps define the true nature of the disease.

No specific therapy is necessary, although it is important to define an etiologic agent, if possible, to prevent recurrence.

Suggested reading

Brannon RB, Fowler CB, Hartman KS. Necrotizing sialometaplasia. A clinicopathologic study of sixty-nine cases and review of the literature. Oral Surg Oral Med Oral Pathol 1991;72:317-25.

Ellis GL, Auclair PL. Tumor-like conditions. In: Ellis GL, Auclair PL, eds. Atlas of Tumor Pathology: Tumors of the Salivary Glands. Fascicle 17. Washington D.C.: Armed Forces Institute of Pathology, 1995:413-19.

From the Department of Endocrine and Otorhinolarynegic-Head and Neck Pathology, Armed Forces Institute of Pathology, Washington, D.C.