Necrotising sialometaplasia is a benign inflammatory condition of the salivary gland remnants or elements, which is usually self-limiting. It is most commonly found on the palate. 

Epidemiology

Most patients are more than 40 years of age, with a male: female ratio of 2:1. It is rarely seen in children. The palate is the most common site involved, usually located in the back of the hard palate.

Clinical presentation

Starts as non-ulcerated swelling with pain. In 2-3 weeks, the necrotic tissue leads to ulcer(s). The condition is usually self-limiting and shows complete remission subsequently without treatment within 6 to 10 weeks.

Pathology

Acinar necrosis is found in early lesions. Subsequently, concomitant squamous metaplasia is seen. Despite necrosis, the lobular architecture of the glands is preserved. Metaplasia may mimic a malignant lesion, hence recognition of this condition is paramount.

Five histological stages have been described: infarction, sequestration, ulceration, reparation and healing.

Despite squamous metaplasia, malignant transformation is very rare.

Aetiology

Aetiology is uncertain, possibly secondary to ischaemia of the salivary tissue leading to infarction. Other postulated causes include:

• abnormal dentures causing chronic irritation to the palate

• following adenoidectomy in children

• prior surgery

• local trauma

• dental injections

• alcohol use

• smoking

• cocaine use

• upper respiratory infections

• radiation

• adjacent tumour growths

• bulimia

Radiographic features

CT

Soft tissue density swelling of the palate which may show ulceration

MRI

They are seen as lobulated submucosal palatal lesions

• T1: hypointense

• T2: hyperintense

• T1 C+: thin peripheral enhancement

Differential diagnosis

Possible differential considerations include

• mucoepidermoid carcinoma

• squamous cell carcinoma

• granulomatous diseases (syphilitic gumma) 

• fungal infections