Abstract

Among the various cartilaginous and osteogenic neoplasms originating in the temporal bone such as osteomas, osteosarcomas, giant cell reparative granulomas and chondrosarcomas, osteomas are commonest benign osseous tumors of temporal bone. Even though osteomas of temporal bone are common, extracanalicular osteomas of the temporal bone are rare. These tumors are slow growing, benign and composed of woven and lamellar bone that is deposited in a cortical pattern with Haversian system. Although they may occur anywhere in temporal bone, they are most common in mastoid region. These tumors are of little significance except for cosmetic deformity.

Introduction

Extracanalicular osteomas of temporal bone are rare. These tumors do not cause many symptoms but are of interest because of cosmetic deformity caused by them. Some times they may be of clinical significance when they cause obstruction of sinus cavity, impinge on brain or eye, interfere with their functions and sometimes if extended in middle ear can cause the conductive deafness. These lesions do not produce serious symptoms but can cause embarrassing cosmetic defect, displacing the pinna, also disturb the symmetry of face.

Case History

Case 1

A 14-year-old female patient presented with swelling behind left ear of 4-year duration (Fig. 1). The swelling was initially painless but patient started feeling pain in the swelling forpast three years. Patient gave no the history of any associated ear discharge, vertigo, vomiting or hearing loss. Local examination revealed a 4.3 cm, single, hard, bosselated swelling, with clearly defined margins situated just behind left pinna, causing it to be pushed laterally and downwards. Skinover the swelling was normal in temperature, stretched but not fixed to the swelling. There was an extension of tumor in the canal causing swelling of posterior external auditory meatal wall. The tympanic membrane was intact audiometric report showed conductive deafness of left ear.

CT scan temporal bone: There was evidence of bony mass arising from the posterior wall and roof of the left external auditory canal. It was continuous with themastoid bone and protruding out. There air cells within the external auditory canal were deformed. The middle ear cavity and inner ear structures were normal. The facial nerve canal was compressed. Significant hematological investigations: Serum calcium - 9.5 mg/dl, PTH - 81.4 pg/ml.

Case 2

A 27-year-old female presented with swelling behind left ear of 2-year duration. This patient gave no complain of pain or any other problem except for cosmetic deformity. The swelling has been gradually increasing in size for past two years. There was noassociated history of ear discharge, headache, vertigo, vomiting or hearing loss. Local examination revealed single circular swelling in postauricular area of approximately 3 cm in diameter, it had smooth surface and overlying skin appeared normal. On palpation, local temperature of skin was normal, swelling was nontender, 3 cm in diameter with bosselated surface, well-defined margins, hard in consistency and fixed to underlying bone. The external auditorycanal was clear and normal, tympanic membrane was intact. Audiometric reportwas normal.

Operative procedure

Both the patients were operated under general anesthesia. The swelling was exposedby incision in midline over swelling and then raising the perichondrial flap. The swellingin both cases were ivory in color, sessile and clear margin of demarcation seen fromunderlying bone. The swelling in each case was drilled out meticulously and completely. The excess skin was trimmed and incision line sutured. Postoperatively, no sign of swelling was seen.Drilling out of this swelling is beneficial as compared to previously used gouge and hammer as there are less chances of contrecoup injury on head, and of facial nerve palsy. It also maintains hemostasis.

Histopathology of tumor

The specimen was composed of fine trabeculae of lamellar bone with occasionalareas of woven bone. Tissue from central part comprised a few maturing cancellous osseoustrabeculae along with fragments of calcifying osteoid issue. Considerable osteoblasticactivity was present with osteoblast extending into stoma. Predominant compact osseoustrabeculae are suggestive of ivory osteoma.

Points to note

In the first case, marked cosmetic deformity was caused by the tumor since, it was pushing the pinna downwards and laterally. The young girl was not able to comb comfortably. Tumor extended upto external auditory canal thus narrowing it as seen in the picture. Excision was thus essential. Tumor was removed with its periosteum to prevent the recurrence. The second case was operated as she was not able to comb her hair and it was also cosmetically disfiguring.

Discussion

Overall, osteoma is a rare tumor of temporal bone.^1-3 External auditory canal is a commonsite of osteoma of the temporal bone. Extracanalicular osteomas are still rarer. They can occur over squama promontory, internal auditory meatus and styloid process. Amongst the extracanalicularosteomas, mastoid appears to be the most prevalent site.

Temporal bone osteomas are more common in females especially over the mastoidprocess.⁴ Here both the cases were females. They occur in young adults but are lesscommon before puberty. The tumor is usually single. Osteoma grows from theouter table of the cortex and an external swelling appears. The etiology of these casesis unknown. Triggering factors are here ditary, trauma and subsequent periostitis may lead to osteomaformation but this was not present in our cases. Superficial osteomas are smooth onpalpation and bony hard in consistency. Skin usually remains normal, although infection may occur. Rarely, pain is a symptom and it is significant, because usually tumor pains when it involves inner table. Osteoma is composed of well-differentiated compact bone of lamellar structure. It has extremely slow growth rate. It is almost restricted to the skull and facial bones from which it may grow into the paranasalsinuses. Radiological diagnosis can be made by plain X-ray in most of cases. Extent ofaccurate location can be determined by various cuts of CT scan. Postoperatively such investigations can be repeated for follow-up. X-ray appearance is that of dense ivory like mass.

Osteomas can be seen as component of Gardener’s syndrome (intestinal Polyposis and soft tissue tumors). Behavior is perfectly benign.

Conclusion

Osteomas are benign lesions and mostly remain asymptomatic, but when causingcosmetic deformity, need active drilling out which is easily managed. CT scan to show its extent is an important tool, which can be done postoperatively and for follow-up also.

References

1. Beale DJ, Phelps PD. Osteomas of the temporal bone: a report of three cases. Clin Radiol1987;38(1):67 9.
2. Clerico DM, Jahn AF, Fontanella S. Osteoma of the internal auditory canal. Case report and literaturereview. Ann Otol Rhinol Laryngol 1994;103(8 Pt 1):619-23.
3. Coates GM. Osteomas growing from the mastoid cortex. Arch Otolaryngol 1938;28(1):27-8.
4. Varshney S. Osteoma of temporal bone. Indian J Otol 2001;7(2):91-2.