Myospherulosis of the Mandible Presenting as a Multilocular Lesion: A Case Report and Review of the Literature

History

A 74 year-old Caucasian female was referred to the oral pathology clinic of our institution by her dentist for the evaluation of an asymptomatic lesion in the right mandibular ramus. The lesion was detected as an incidental finding on a routine panoramic radiograph. The patient denied having any previous surgery in the involved area, aside from an uneventful third molar extraction in her youth. Her relevant medical history includes high blood pressure, eczema and alleged contact allergies to certain metals. She does not smoke or drink alcohol. Clinically, there was no expansion of the cortices or any significant mucosal anomaly.

Radiographic Features

A panorex and a cone-beam computed tomography (CBCT) were ordered and showed a well-defined, non-expansile, multilocular radiolucency of the right posterior mandible, above the lower alveolar nerve (Fig. 1a, c). The anterior portion of the lesion was in continuity with an area of diffuse medullary sclerosis, consistent with localized condensing osteitis. Surgical exploration and a bone biopsy were performed under local anesthesia after informed consent. During the procedure, a lobulated cavity was identified and contained a black, viscous, tar-like substance (Fig. 2). The mandibular lingual cortex was eroded in several areas (Fig. 1b, d). There was no cystic lining or any other sign of pathology.

Fig. 1.

a Panoramic view of the right mandibular ramus presenting as a multilocular radiolucency, located above the lower alveolar nerve. b Coronal, c vertical oblique and d axial views of CBCT displaying a multilocular lesion in the right mandibular ramus

Fig. 2.

Oil-based substance removed from bone and floating in buffered formalin

Diagnosis

Histologically, the entire specimen consisted of black spherules of varying size, admixed with amorphous eosinophilic debris, consistent with a diagnosis of myospherulosis (Fig. 3). The whole cavity was conservatively debrided and the patient showed no sign of recurrence 7 months later.

Fig. 3.

Characteristic histologic appearance of black spherules of varying size and amorphous eosinophilic debris (hematoxylin-eosin, magnification ×20)

Discussion

Myospherulosis, also known as spherulosis or spherulocytosis, consists of a rare foreign-body reaction in tissues more often resulting from a contact with petrolatum-based products. The diagnosis of myospherulosis is confirmed by histology and can be detected by imagery. Myospherulosis has been reported in various anatomic sites, including the nose, paranasal sinuses, eye, upper eyelid, oral cavity, lower lip, brain, liver, skin, breast and kidney [1–10].

Myospherulosis was initially reported by McClatchie et al. in 1969 [4]. The condition was termed “myospherulosis” because of its location in skeletal muscle and histologic features. The latter includes the formation of “spherules”, which appear in cystic-like spaces, known as “parent bodies”. Foreign body-type giant cells and eosinophilic infiltrates may be present [7].

The first case of myospherulosis in the United States was identified by Kyriakos in 1977 [1]. He described sixteen cases of “spherulosis” lesions in areas of previous surgery in the nose, paranasal sinuses and middle ear. The causative agent was thought to be an unidentified endosporulating fungus. His hypothesis emerged from the common surgical use of gauzes filled with unsterilized petrolatum-based antibiotic ointment.

A year later, Rosai [11] stipulated that the spherules were not actually of fungal origin but rather derived from the contact of erythrocytes with lipid-containing material, the brownish color being due to the degradation of hemoglobin.

The first cases involving the jaws were reported in 1980 by Dunlap and Barker [12]. Later, Lynch et al. [13] reported six additional cases in the oral cavity.

Most cases of oral myospherulosis are thought to originate from the use of tetracycline-containing petrolatum-based ointments at the site of dental extractions. Antibiotic ointments are usually placed in the alveolar bone in order to prevent alveolar osteitis. This practice is controversial and the efficiency of petrolatum-based ointments remains to be statistically demonstrated [14]. Most cases of myospherulosis appear to be iatrogenic in origin, although other factors may be linked, such as the release of endogenous lipids via trauma and, putatively, parasitic infection [15]. Sindwani et al. [16] suggest that patients who develop myospherulosis could have lipid sensitivity and display a greater tendency towards immune-mediated reactions.

Myospherulosis of the jaws typically occurs within bone, at the site of extraction of mandibular third molars [17]. It is usually discovered as an incidental finding on dental radiographs, and may present clinically as an asymptomatic soft tissue swelling. In rare cases, patients may present pain and purulent discharge. Surgical exploration reveals black, greasy, tar-like foreign material in association with a bony defect [18]. Radiographically, myospherulosis presents as a well-circumscribed unilocular radiolucency, although our case presented as an extremely unusual multilocular radiolucency. The differential diagnosis for multilocular radiolucencies includes the following: ameloblastoma, odontogenic myxoma, odontogenic keratocystic tumour (odontogenic keratocyst), cherubism, central giant cell granuloma, central mucoepidermoid carcinoma, hemangioma and other rare lesions (Table 1). In our opinion, this list should include myospherulosis, whenever there is a history of previous extraction, especially the site of mandibular third molars. Surgical exploration and biopsy is required for final diagnosis. Myospherulosis might be overlooked in dentistry on account of its rare occurence and lack of associated symptoms.

Table 1.

Differential diagnosis for multilocular radiolucencies of the jaws

	Site of predilection	Typical radiographic features
Myospherulosis	Mandible	Non-expansile
Ameloblastoma	Mandibular molar-ramus area	Expansile with thick, angulated septae
Odontogenic keratocystic tumour	Mandibular molar-ramus area	May be multifocal in Gorlin syndrome
Cherubism	Posterior mandibule and maxilla	Symmetrical and bilateral
Central giant cell granuloma	Mandibular region, anterior to first permanent molar	May be multifocal in hyperparathyroidism Fine septae at a 90° angle and expansile
Odontogenic myxoma	Mandibule	Fine septae at a 90° angle and expansile “Honeycombed” pattern
Hemangioma	Mandibule, zygoma and orbital region	Expansile
Central mucoepidermoid carcinoma	Mandibule	Expansile
Botryoid odontogenic cyst	Anterior region of mandible	Well-delineated “grape-like” pattern

Treatment of myospherulosis consists of complete conservative removal of the foreign material with curettage of the affected area. Recurrence is rare. All excised tissue should be submitted for histopathologic examination in order to rule-out superimposed pathologies, such as aspergillosis [19]. Immunostaining for hemoglobin or antibody-based staining methods may be used to distinguish myospherulosis from endosporulating organisms, such as Coccidioides and Rhinosporidium seeberi [20].

The common denominator of myospherulosis in the literature is the use of a topical antibiotic ointment [12, 17, 21–23]. This raises questions on the safety of antibiotic ointments. Water-soluble antibiotic pastes, as opposed to petrolatum-based ointments, may reduce the risk of granulomatous foreign-body reactions [16, 24], but there is no clear evidence that myospherulosis may be avoided.

Compliance with Ethical Standards

Conflict of interest

All authors declare that there are no financial conflicts associated with this report and that there is no funding source.