Benign Osteoblastoma of the Temporal Bone: Case Report and Literature Review Salil V. Doshi, MD, Timothy D. Frantz, MD, and Harold W. Korol, MD We report a case of benign osteoblastoma of the temporal bone and a review of the literature. Osteoblastoma is a rare bony tumor that usually develops in the long bones or in the vertebral column. To our knowledge, this is the fourth reported case of benign osteoblastoma confined to the temporal bone, and it is the second such reported case to include facial paralysis as the initial symptom. Result of computed tomography scan, magnetic resonance imaging scan, and angiography are reported. The diagnosis and management of this type of lesion are also discussed. (Am J Otolaryngol 2001;22:211-214. Copyright © 2001 by W.B. Saunders Company) (Editorial comment: The authors present the conservative approach to treatment of this rare tumor.)
Osteoblastoma is an uncommon condition, representing only 1% of all bone tumors. Osteoblastoma confined to the temporal bone is extremely rare; to our knowledge, only 3 cases have been reported. We report the fourth known case of osteoblastoma affecting only the temporal bone, only the second such case to include facial paralysis as the initial symptom. CASE REPORT A 19-year-old female patient was first seen for a 1-month history of progressive hearing loss and pulsatile tinnitus in the right ear. The patient denied any pain, pressure, or vertigo, but had transient right facial paralysis approximately 3 months before. The medical history was clinically significant only for a congenital anomaly of the right hand. Physical examination results showed a soft, reddish mass completely occluding the right external auditory canal. The left external auditory canal and tympanic membrane appeared normal. No cranial nerve deficits were noted. The Weber
From the Department of Head and Neck Surgery, Kaiser Permanente Medical Center, Redwood City, CA. Presented at the annual meeting of the Pacific Coast Oto-Ophthalmological Society, June 18-22, 1994, Huntington Beach, CA. Address reprint requests to Harold W. Korol, MD, Department of Head and Neck Surgery, Kaiser Permanente Medical Center, 1150 Veterans Blvd, Redwood City, CA 94063-2087. Copyright © 2001 by W.B. Saunders Company 0196-0709/01/2203-0009$35.00/0 doi:10.1053/ajot.2001.23432
test showed lateralization to the right ear. Examination of the remainder of the head and neck showed no abnormalities. Concurrent routine audiometry showed a 30- to 40-dB flat conductive hearing loss in the right ear and normal hearing in the left ear. The patient had speech reception thresholds of 40 dB in the right ear and 0 dB in the left ear. Speech discrimination scores were excellent bilaterally. Computed tomography (CT) scan of the temporal bone showed soft tissue extending medially and inferiorly within the bony portion of the right posterior external auditory canal (Fig 1), and bony destruction of the hypotympanum immediately lateral to the jugular bulb. A magnetic resonance imaging (MRI) scan showed an enhancing softtissue mass in the right lateral petrous portion of the temporal bone and bony destruction of the floor of the middle ear cavity and hypotympanum (Fig 2). These results were consistent with glomus tympanicum tumor or glomus jugulare tumor. Angiography showed moderate neovascularity but did not show the tumor blush that is characteristic of a glomus tumor (Fig 3). We attempted biopsy of the mass through the external auditory canal but encountered moderate bleeding and obtained a nondiagnostic specimen. After consulting with the patient and her family, we proceeded with surgery and intraoperative monitoring of the facial nerve using manual pressure and an absorbable gelatin sponge to control blood flow in the surgical field. During the operation, a mulberry-shaped, light purple mass, covered with a thin layer of bone, was seen in the mastoid cavity. The lesion surrounded the facial nerve from the second genu to its exit at the stylomastoid foramen and abutted the sigmoid sinus and jugular bulb. Using a facial recess approach, we saw no extension of the process into the middle ear. A diamond burr and curet were used to decompress the vertical portion of the facial nerve. Subtotal resection was done, deferring more extensive surgery pending final diagnosis. Estimated blood loss during the pro-
American Journal of Otolaryngology, Vol 22, No 3 (May-June), 2001: pp 211-214
DOSHI, FRANTZ, AND KOROL
ual soft tissue in and below the bony external auditory canal and adjacent to a defect in the posterior canal wall. We proceeded with revision mastoidectomy, which showed no residual osteoblastoma in the mastoid cavity. A firm bony plate lateral to the tympanic membrane was then removed. The patient was asymptomatic at 15-month follow-up and had complete closure of the air-bone gap in the right ear. A CT scan showed no evidence of recurrent soft tissue in the right temporal bone (Fig 5).
Preoperative CT scan of temporal bone.
cedure was 250 mL. The patient had normal facial nerve function postoperatively. The surgical specimen showed osteoblastic and osteoclastic activity, as well as mature and immature bone. The preliminary diagnosis was consistent with osteoid osteoma or osteoblastoma (Fig 4). Six weeks after surgery, the tinnitus had abated; however, the conductive hearing loss in the right ear persisted. Because of persistent posterior canal wall deformity, the tympanic membrane could not be completely visualized. A CT scan showed resid-
Fig 2. Preoperative MRI scan of temporal bone. Note soft-tissue mass in right external auditory canal.
Osteoblastoma was described in 1956 by Lichtenstein1 and Jaffe,2 according to whom the tumor is distinguished from others (including osteogenic fibroma) by its osteoblastic, nonfibroblastic nature. The tumor usually occurs in children and young adults but has been described in all age groups and without notable gender predilection.1 Usually found in the long bones or the vertebral column, osteoblastoma may affect the skull3 in 15% to 20% of cases. Symptoms include
Fig 3. Anteroposterior view of angiogram. Arrow denotes areas of increased vascularity corresponding to tumor.
BENIGN TEMPORAL BONE OSTEOBLASTOMA
Fig 4. Overview of osteoblastoma of temporal bone (hematoxylin and eosin stain, original magnification ⴛ63).
dull, aching, localized pain, frequently with soft tissue edema and erythema overlying the tumor.4,5 Benign osteoblastoma is a well-circumscribed but nonencapsulated tumor with marked vascularity and gritty texture. The tumor shows a trabecular pattern of osteoblastic and osteoclastic activity around osteoid and new bone, as well as numerous identical round or ovoid cells with distinct cytoplasmic borders. Multinucleated giant cells, but no atypia and few mitoses, are present. Numerous thin-walled vascular channels also are seen.1 Benign osteoblastoma appears radiographically to be well circumscribed but may expand throughout the bone.5 The area of cortical erosion is generally surrounded by a thin shell of new bone. The lesion may appear radiolucent, mottled, or even radiopaque, especially after radiation treatment.6 Younger lesions may appear more radiolucent, but ossify as they mature.7 Nuclear technetium scanning may show the thin cortical shell typical of new bone growth more efficiently than other imaging techniques5,8; angiography may show increased vascularity more efficiently than other techniques.5 Benign osteoblastoma may be closely related to osteoid osteoma and is differentiated from it on the basis of size: osteoid osteoma tumors are typically less than 1 cm; osteoblastoma tumors, more than or equal to 1 cm.6 Osteoblastoma often is more vascular than osteoid osteoma and is shown radiographically to expand more aggressively through
cortical bone.4,7 Osteoid osteoma is surrounded by more sclerotic bone, and x-ray films may show a thin central nidus.5 Osteoid osteoma can also be more painful than osteoblastoma. A more important distinction to be made is between osteoblastoma and osteosarcoma. The latter is more aggressive and causes greater bone destruction. This behavior may be difficult to assess radiographically. Osteosarcoma displays greater cellular atypia, mitotic activity, and cartilage proliferations than osteoblastoma.4,7 Benign osteoblastoma is treated conservatively because the lesion behaves in a benign fashion. Curettage (with or without packing of the cavity with bone chips) or conservative resection should be sufficient.5 Although up to 20% recurrence is seen when this treatment is used, most investigators have reported complete tumor regression.5,9 Lichtenstein1 recommended that osteoblastoma of the spinal column should receive additional radiation treatment to prevent cord compression; however, radiation may induce malignant degeneration of a previously benign tumor.4 A locally aggressive variant with more large epithelioid osteoblasts has been reported; it is more mitotically active, shows multifocal growth, and is more aggressive locally but does not metastasize.7,10 Benign osteoblas-
Fig 5. Postoperative CT scan 15 months after procedures. Note postoperative changes but no evidence of recurrence of soft tissue in temporal bone.
toma has rarely been reported to become malignant.7 To our knowledge, this is the 10th reported case of osteoblastoma of the temporal bone, the fourth reported case of osteoblastoma affecting only the temporal bone, and only the second such case reported as having facial paralysis as the initial symptom. Important diagnostic features include hearing loss arising from an affected middle ear or ossicle, facial paralysis and facial nerve compression, or pain and swelling. Diagnosis may be difficult because of insufficient clinical experience with this uncommon lesion. We emphasize the need for conservative treatment, which can be expected to have a favorable outcome. ACKNOWLEDGMENT The Medical Editing Department, Kaiser Foundation Research Institute, provided editorial assistance.
DOSHI, FRANTZ, AND KOROL
REFERENCES 1. Lichtenstein L: Benign osteoblastoma: A category of osteoid- and bone-forming tumors other than classical osteoid osteoma, which may be mistaken for giant-cell tumor or osteogenic sarcoma. Cancer 9:1044-1052, 1956 2. Jaffe HL: Benign osteoblastoma. Bull Hosp Joint Dis 17:141-151, 1956 3. Ronis ML, Obando M, Bucko MI, et al: Benign osteoblastoma of the temporal bone. Laryngoscope 84:857863, 1974 4. Potter C, Conner GH, Sharkey FE: Benign osteoblastoma of the temporal bone. Am J Otol 4:318-322, 1983 5. Clutter DJ, Leopold DA, Gould LV: Benign osteoblastoma: Report of a case and review of the literature. Arch Otolaryngol 110:334-336, 1984 6. Gellad FE, Hafiz MA, Blanchard CL: Osteoblastoma of the temporal bone: CT findings. J Comput Assist Tomogr 9:577-579, 1985 7. Lucas DR, Unni KK, McLeod RA, et al: Osteoblastoma: Clinicopathologic study of 306 cases. Hum Pathol 25:117-134, 1994 8. Miyazaki S, Tsubokawa T, Katayama Y, et al: Benign osteoblastoma of the temporal bone of an infant. Surg Neurol 27:277-283, 1987 9. Matsumoto K, Kakita K, Fukuma S: Large, benign osteoblastoma of the temporal bone: Case report. Neurol Med Chir (Tokyo) 29:444-448, 1989 10. Adler M, Hnatuk L, Mock D, et al: Aggressive osteoblastoma of the temporal bone: A case report. J Otolaryngol 19:307-310, 1990