Actinomyces-associated Calcification in a Nasopalatine Cyst

A 51-year-old male was referred by his general dental practitioner (GDP) for assessment and management of a tender swelling in his anterior hard palate. The patient's medical history was unremarkable. The patient reported a previous acute episode of swelling, with foul tasting discharge, for which his GDP had empirically prescribed a 5-day course of 500 mg amoxicillin three times daily. The antibiotic therapy reduced symptoms, but was not successful in alleviating the swelling. There were neither previous symptoms from the area, nor history of dental trauma.

The specific examination found the anterior hard palate mucosa to be tender to finger palpation with the presence of a sinus tract in the incisive papilla. The maxillary incisor teeth were unrestored, gave normal responses to pulp sensibility tests and had a periodontal probing profile that was within normal limits. There was mild anterior tooth surface loss, which was judged to be attritive in character, and associated with nocturnal parafunction as the major aetiological factor.

A long-cone peri-apical (LCPA) digital radiograph (Figure 1) revealed the presence of a radiolucency between the apices of the upper left and right maxillary incisors, within the region of the incisive foramen.

A well-defined radiopaque 3.5 x 5 mm mass was centred within this radiolucent area. Cone-beam computed tomography (CBCT) confirmed the radiolucency to be an enlarged incisive canal with the presence of the radiopaque object on the palatal aspect (Figures 2 and 3). The radiopacity of the object was similar to enamel, but there were no morphological features that would have been consistent with the lesion having dental origins.

The differential diagnoses included: nasopalatine cyst with dystrophic calcification; dentigerous cyst of ectopic supernumerary tooth; minor salivary gland stone; minor salivary gland neoplasm with calcification;¹ and, odontoma. Secondary infection with Actinomyces species (as the cause for the dystrophic calcification) was not initially considered.

The case was managed via the use of CBCT examination to precisely locate the position and extent of the lesion, followed by excisional biopsy, under local anaesthetic, of both the soft- and hard-tissue components. Surgical access was via a full-thickness palatal muco-periosteal flap (Figure 4) with curettage of granulation-type tissue and the removal of a brown/black hard object (Figure 5), which was submitted for histopathological diagnosis. The flap was repositioned and closed with 6-0 nylon monofilament sutures. Healing was uneventful, and at the 10-day review the patient reported alleviation of symptoms.

Processing of the material for histopathology included staining with haematoxylin and eosin. Colonies of Actinomyces species were well demonstrated within the material, confirming the diagnosis as a nasopalatine duct cyst with secondary actinomyces infection and dystrophic calcification.

Discussion

Nasopalatine cysts are the most prevalent non-odontogenic cyst of the jaw, occurring in up to 1% of the population.² These lesions are often asymptomatic until large, but symptoms of tenderness and rapid swelling can accompany secondary infection. Enucleation is often curative.

Actinomycosis is a rare chronic bacterial infection caused by Actinomyces species, which are Gram-positive anaerobic or micro-aerophilic bacilli with a tendency to form a branching filamentous structure.³ Classically, within Actinomyces infections, small ‘sulphur granules’ may be feature (named after their sulphurous appearance rather than content), which represent large colonies of the bacteria.⁴Actinomyces are commensals of the human oropharynx and can invade local structures when mucosal integrity is breached.⁴ The authors considered it likely that in this case the Actinomyces infection became established via a tract formed between the mouth and (discharging) nasopalatine cyst. Within an actinomycosis lesion, chronically inflamed and necrotic tissue may undergo dystrophic calcification⁵ owing to the precipitation of mineral salts within this material. The resultant calcifications have been described as ‘popcorn-like’ in shape.^5,6 The black colouration of Actinomyces-associated calcifications has been hypothesized to arise from incorporation of products derived from local haemorrhagic events.⁷ While the finding of calcifications associated with an Actinomyces-infected dentigerous cyst has been previously reported,⁷ to the authors' knowledge, the presence of dystrophic calcification within an Actinomyces-infected nasopalatine cyst has not been previously documented. As part of the diagnostic work-up, and to aid in the selection of an appropriate antimicrobial therapy (where indicated), a sample of pus may be submitted for culture and sensitivity testing (although this was not undertaken in this particular case). However, while various antibiotic regimens (often of long duration) have been suggested for the management of actinomycosis, this therapy in itself is not always curative and early surgical removal of the lesion has been recommended.⁸ The requirement for surgical intervention to manage actinomycosis infections is increased if histopathological examination is required, or if there is associated disease, such as the presence of a cystic lesion.

Conclusion

Within an actinomycosis lesion, chronically inflamed and necrotic tissue may undergo dystrophic calcification, and where relevant, should be considered within the differential diagnoses of such presentations. Onward referral to relevant secondary or tertiary care providers should be instituted where the nature of a lesion cannot be determined or predictably managed within a primary care setting.