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Osseous metaplasia of the maxillary sinus with formation of a well-developed haversian system and bone marrow.


Osteogenesis in the maxillary sinus is a lesser known entity in otolaryngology, although it is put to good therapeutic use by maxillofacial surgeons. We present a case of postoperative osseous metaplasia in the maxillary sinus that led to the formation of mature bone with a well-developed haversian system and bone marrow. Such a finding has not been previously reported as a complication of endoscopic sinus surgery. This case highlights the importance of keeping in mind the possibility of osteogenesis within the maxillary sinus in patients who experience a recurrence of symptoms following sinus surgery.


Bone formation in the paranasal sinuses in the form of an osteoma is well known. Such a growth is commonly seen in the area of the frontoethmoid sinuses; only 5% of such cases occur in the maxillary sinuses. (1) Osteogenesis that produces formation of bone other than an osteoma in the maxillary sinus has also been documented in association with sinus lift procedures for the placement of dental implants.

We present a case of osseous metaplasia that led to the formation of bone with a well-developed haversian system and bone marrow in the maxillary sinus following endoscopic sinus surgery. A systematic search of the literature did not reveal any similar case. We believe that this is the first reported case of osseous metaplasia within the maxillary sinus that was triggered by endoscopic sinus surgery. We also describe the diagnostic and treatment challenges we faced.

Case report

A 47-year-old man first presented to our Department of Otorhinolaryngology with a complaint of left-sided facial pain. The initial examination revealed the presence of a deviated nasal septum to the left. Magnetic resonance imaging (MRI) detected a retained tooth root and an expansile mass in the left maxillary antrum that was suggestive of a mucocele (figure 1). The patient underwent a left-sided middle meatal antrostomy and removal of the last two left-upper molars. He experienced no postoperative complications. Staphylococcus aureus was cultured from the left maxillary sinus contents, and the patient was treated accordingly.

Postoperatively, the patient's symptoms persisted; in addition, he also developed intermittent nasal bleeding. Computed tomography (CT) of the sinuses demonstrated a completely opacified maxillary antrum with areas of calcification suggestive of fungal sinusitis (figure 2). Therefore, 2 years after his initial presentation, the patient underwent an attempted surgical exploration of the left maxillary sinus. Attempts were made both endoscopically and via a Caldwell-Luc approach, but neither type of exploration was possible because the maxillary sinus was found to be full of dense bony material that could not be removed. Culture and histology of the sinus contents detected evidence of a cholesterol granuloma but no fungal material. Follow-up CT again showed opacification of the left maxillary sinus with areas of ossification. The patient's facial pain abated, and he was followed with observation.


One year later, the patient reported a recurrence of his left-sided facial pain along with heaviness over the left side of his face. CT of the sinuses again demonstrated a ring of thick calcification within the sinus cavity in addition to a loss of sinus cavity volume (figure 3). The patient underwent another Caldwell-Luc procedure, and this time the bony lesion was completely removed. Histopathologic examination of the specimen revealed fragments of lamellar bone covered with respiratory mucosa that exhibited mild chronic inflammation and fibrosis of the lamina propria (figure 4). The lamellar bone showed a well-developed haversian system and fatty bone marrow. There were fragments of mature fibrous tissue with numerous cholesterol clefts, siderophages, and foci of dystrophic calcification. Follow-up CT 2 months postoperatively did not detect any recurrence.


Metaplasia is the conversion of one fully differentiated cell type to another fully differentiated cell type. Metaplasia has been known to occur in both epithelial tissue and connective tissue. Osseous metaplasia is a type of connective-tissue metaplasia that is often seen in scars, bronchi, the urinary bladder, etc. There have also been reports of osseous metaplasia occurring in the cardiac valves (2) and gastrointestinal tract. (3)


Bone formation in the maxillary sinus is well known, and formation ofosteomas in the maxillary sinus following surgical procedures has been documented. (1) Lundgren et al reported bone formation in the maxillary sinus as a result of surgical trauma and the creation of a secluded space between the bone surfaces and sinus mucosa. (4)

In our patient, the differential diagnosis varied at different stages of disease progression. In the beginning, our differential diagnosis was based on CT findings, and it included fungal sinusitis and chronic bacterial maxillary sinusitis. As reported by Yoon et al, scans that demonstrate round or eggshell calcifications are seen only in patients with nonfungal sinusitis. (5) Eggshell-like bony capsules may also be seen in ossifying fibromas and cemento-ossifying fibromas, (6) which are monostotic expansive tumors that are known to occur in the maxillary sinus. (7)



In our case, findings on subsequent imaging coupled with operative findings brought the diagnosis of osteoma and ossification into consideration. Osteomas are bone-forming tumors, and their occurrence in the maxillary sinus following dental extraction and surgery for oroantral fistulas has been documented in the literature. (8) We ruled out osteoma on the basis of three findings: (1) our initial surgical procedure was not complicated by the formation of an oroantral fistula; (2) the lesion demonstrated a central soft-tissue opacity on imaging; and (3) examination of the excised specimen revealed a hollow center.

The pathogenesis of ossification in the maxillary sinus is still unclear. Some authors have theorized that skeletal trauma might play a contributory role, but others have proposed that previous inflammation may play a determinant part. In our patient, both of these theories seemed to be applicable. Our patient had an initial history suggestive of maxillary sinusitis that was treated with surgical intervention. The inflammation appeared to have provided the initial stimulus for osteoblastic proliferation, which was then boosted by surgical intervention. In the human body, skeletal trauma during endoscopic sinus surgery is followed by a normal reparative attempt that involves the recruitment of osteoblasts. In our patient, bleeding in the sinus as evidenced by the cholesterol clefts on histopathologic examination provided the various growth factors needed for osteogenesis. We believe that multiple contributory factors played an important role in his osseous metaplasia. There are probably other unknown contributory factors; nearly all patients who undergo sinus surgery have the above-mentioned stimuli, but we rarely encounter sinus ossification in them.

We have presented this case of osseous metaplasia as a highly unusual sequela of endoscopic sinus surgery, which we believe was the primary surgical insult that triggered the process of ossification. We should therefore bear in mind the possibility of osteogenesis in the maxillary sinus when CT shows calcification.


(1.) Moretti A, Croce A, Leone O, D'Agostino L. Osteoma of maxillary sinus: Case report. Acta Otorhinolaryngol Ital 2004;24(4):219-22.

(2.) Fernandez Gonzalez AL, Montero JA, Martinez Monzonis A, et al.

Osseous metaplasia and hematopoietic bone marrow in a calcified aortic valve. Tex Heart Inst J 1997;24(3):232.

(3.) Al-Daraji WI, Abdellaoui A, Salman WD. Osseous metaplasia in a tubular adenoma of the colon. J Clin Pathol 2005;58(2):220-1.

(4.) Lundgren S, Andersson S, Sennerby L. Spontaneous bone formation in the maxillary sinus after removal of a cyst: Coincidence or consequence. Clin Implant Dent Relat Res 2003;5(2):78-81.

(5.) Yoon JH, Na DG, Byun HS, et al. Calcification in chronic maxillary sinusitis: Comparison of CT findings with histopathologic results. AJNR Am J Neuroradiol 1999;20(4):571-4.

(6.) Bertrand B, Eloy P, Cornelis JP, et al. Juvenile aggressive cementoossifying fibroma: Case report and review of the literature. Laryngoscope 1993;103(12):1385-90.

(7.) Magu S, Airon RK, Mishra DS, et al. Images: Cementoossifying fibroma of the maxilla. Indian Journal of Radiology and Imaging 2000;10(2):103-4.

(8.) Sudhoff H, Theegarten D, Luckhaupt H. Osteoma of the maxillary sinus [in German]. Laryngorhinootologie 2001;80(5):275-7.

Suchir Maitra, DLO, DOHNS; Deepak Gupta, FRCS; Miladvic Radojkovic, MD; Salil Sood, MS

From the Department of Otorhinolaryngology (Dr. Maitra, Dr. Gupta, and Dr. Sood) and the Department of Pathology (Dr. Radojkovic), Great Western Hospital, Swindon, U.K.

Corresponding author: Deepak Gupta, Consultant ENT Surgeon, Department of Otorhinolaryngology, Great Western Hospital, Swindon, Wiltshire SN3 6BB, UK. E-mail:
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Article Details
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Author:Maitra, Suchir; Gupta, Deepak; Radojkovic, Miladvic; Sood, Salil
Publication:Ear, Nose and Throat Journal
Article Type:Report
Geographic Code:4EUUK
Date:Sep 1, 2009
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