Case Report: Necrotising Sialometaplasia
Necrotising sialometaplasia is a benign, self-limiting, inflammatory condition. This rare lesion has a range of clinical presentations but can resemble malignant lesions both clinically and histopathologically resulting in issues with correct diagnosis. We present the case of a 54 year old female patient who was referred from her dentist for a round white patch on her right soft palate that had been increasing in size. This was diagnosed as necrotising sialometaplasia following a biopsy and clinicopathological correlation. The lesion took four months from when first noticed by the patient to fully heal.
Necrotising sialometaplasia is a rare, benign, self-limiting, inflammatory condition which can mimic, both clinically and histopatholigcally, malignant lesions such as squamous cell carcinoma or mucoepidermoid carcinoma (1). The condition is relatively rare, as described by one study published in 1984, which identified necrotising sialometaplasia in just 0.03% of 10,414 biopsies carried out over a 10 year period (2). Although they did note that this number may be under-represented relative to the total incidence, given that some presentations were not biopsied (2). This lesion most commonly presents in middle-aged adults; men more than women with reported ratios varying: 1.9:1, 2:1, 5.9:1, 7.7:1 (1 d.p.) (1, 3-6).
Necotising sialometaplasia can present wherever salivary gland tissue is present, such as the labial/buccal mucosa, retromolar trigone, floor of mouth, maxillary sinus and tonsillar fossa; an estimated 80% of cases affect the minor salivary glands of the palate (1, 3, 6). These lesions typically arise as a 1.5-2cm diameter swelling on the posterior hard palate which then ulcerates with irregular everted margins (3, 4). Whilst typically unilateral, differing figures of 12% and 20% have been reported accounting for bilateral presentations (1, 3, 5).
Due to the similar appearance of necrotising sialometaplasia to cancerous lesions there is a risk of misdiagnosis and subsequent overtreatment. Hence, correctly identifying such lesions is pertinent to avoid unecessary surgery. This report describes a case of a 54 year old female who presented with a non-healing ulcerative lesion which was later identified as necrotising sialometaplasia.
A 54 year old female patient was referred to Addenbrooke’s Oral and Maxillofacial Surgery department along the suspected cancer pathway for an enlarging round white patch on the right soft palate.
The patient had first noticed the lesion approximately a month prior to her initial presentation. The area had been intermittently symptomatic, at worst 5/10 in pain severity, with an associated bad taste. She reported dysesthesia of the lesion when using e-cigarettes and eating spicy foods. There was no reported history of trauma or recurring ulcers, no dysphagia or odynophagia, no extraoral symptoms, and no facial swelling or numbness. She had experienced no recent unexplained weight loss and felt well within herself. A recent five-day course of amoxicillin from her GP resulted in symptom improvement.
This patient reported a history of chronic obstructive pulmonary disease for which she used a beclometasone/formoterol inhaler twice daily, tiotropium bromide once daily and a salbutamol inhaler as required. She was using a spacer device with her inhalers but was not rinsing after use. She was taking lansoprazole for acid reflux and also suffered from osteoarthritis and diverticular disase. She had no known allergies and was a non-drinker. She reported using e-cigarettes with tobacco-containing liquid three to four times a day.
Upon first clinic attendance there was a soft, non-scrapeable, well-circumscribed, superficially ulcerated oval lesion 2cmx1cm with surrounding erythema on the right soft palate. This lesion was tender to palpation and there was an adjacent small white spot posteriorly (Figure 1).
An orthopantomogram (OPG) radiograph was taken to rule out the white spot being a draining sinus, as there was an adjacent grade II mobile upper right third molar (UR8). The resultant OPG showed generalised horizontal bone loss of approximately 20-50%, a retained lower left second deciduous molar (LLE) but no radiolucencies to indicate periapical pathology of the dentition (Figure 2).
Our provisional diagnosis at this time was major aphthous ulceration. It was still important to rule out a malignancy due to the patient’s use of tobacco, and a persistence of over two weeks.
We advised the patient to start rinsing after inhaler usage and arranged an incisional biopsy under local anaesthetic. When the patient attended for her biopsy 7 days later she was reporting worsening dysgeusia and the lesion had become more sinister looking, with raised rolled edges, and a more deeply ulcerated appearance (Figure 3).
The histopathology report came back showing extensive ulceration with full thickness coagulative/ischaemic necrosis of adjacent squamous epithelium including the superficial lamina propria. The necrotic epithelium was partly detached. The ulcer bed extended into an underlying minor salivary gland. The HHV8, CMV, HSV and EBER/EBV immunostains were all negative. No bacteria, including acid fast bacteria, fungi or parasites were identified with histochemical stains.
Clinicopathological correlation was advised to reach the definitive diagnosis as several differentials were suggested by the histopathologist as being responsible for this mucosal ulceration with ischemic necrosis. These included a drug reaction, erythema multiforme, toxic epidermal necrolysis and exogenous mechanical/heat damage.
At the review appointment three weeks following the biopsy, four weeks post initial presentation, we observed a 1cmx8mm palatal defect with surrounding erythema at the lesion’s biopsy site. The 1.7x1.7cm lesion adjacent to the biopsy site had a shallow yellow base with an erythematous outline and appeared to be healing relative to previous clinical photographs (Figure 4). The palate was still tender to palpation but was soft with no induration. The patient reported they had been very sore post-biopsy, but their condition was improving. We informed them of our new provisional diagnosis of necrotising sialometaplasia and advised to continue with warm salt mouth rinses three times daily and good oral hygiene until the area had healed.
A further review was arranged for two months later, three months post initial presentation, at which point the lesion had fully healed spontaneously (Figure 5). The patient was subsequently discharged back to the care of her GMP and dentist.
This case demonstrates the interesting course of a rare inflammatory disease, and the likeness to its more sinister differentials. The differentials for necrotising sialometaplasia include a traumatic ulcer, mucoepidermoid carcinoma, squamous cell carcinoma, a syphilitc ulcer, a tuberculous ulcer and an invasive fungal infection in an immunosuppressed patient (1).
The exact aetiology of necrotising sialometaplasia is unknown but multiple predisposing factors have been linked to the condition including chronic vomiting, direct trauma, smoking, a compromised immune system, ill-fitting dentures, cocaine abuse and local anaesthesia infiltration (1, 6-8).
Histopathological examination of necrotising sialometaplasia shows lobular ichaemic necrosis and inflammation. Also often seen is a hyperplastic healing response of the ducts and acini which can mimic a carcinoma. This is due to squamous metaplasia of the ducts and acini resulting in the formation of islands of epithelium (4, 7). Biopsies may show pseudoepitheliomatous hyperplasia which can also lead to the misdiagnosis of a carcinoma (1, 3, 6).
There are a set of criteria, first described in 1973, which help to histologically distinguish this lesion from its malignant differentials, including: lobular necrosis, no nuclear pleomorphism characteristic of a malignancy, metaplasia of ducts and mucinous acini, granulation tissue and inflammatory infiltrate, and maintenance of general tissue architecture (7). Use of such criteria is necessary to avoid misdiagnosis which could result in unnecessary surgical intervention, a risk which is also increased when biopsies taken are too small or superficial (3, 4).
As shown in this case, despite the distressing presentation, this condition is self-resolving. In our patient’s case the lesion took around 4 months to fully resolve from when first noticed. However, average reported healing times in literature have typically varied between 4-10 weeks (1, 5, 6, 8, 9). The clinical timecourse is also matched to a pathological timecourse, with five histological stages having been proposed by Anneroth and Hansen in 1982: infarction, sequestration, ulceration, repair, and healed (1, 9). Management is typically limited to eliminating/minimising risk factors. In this case pertaining to the patients use of e-cigarettes, but may also include the use of 0.2% chlorhexidine gluconate mouthwash or gel to reduce risk of secondary infection and control inflammation (8). There have also been reported cases where management involved topical and systemic steroids (5).
Our case report highlights a presentation of a relatively rare inflammatory condition – necrotising sialometaplasia. Despite its close clinical and histological mimics to squamous cell carcinoma and mucoepidermoid carcinoma, this disease is instead benign inflammation following ischaemic necrosis of salivary gland tissue. Our report highlights the interesting course of this self-resolving disease, and thus, the need for a careful diagnosis to avoid unecessary invasive surgical treatment.
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