2. History 20 year old lady who fell and hit her head about 12 months prior to presentation Sustained a small right frontal skull swelling. The swelling remained static in size until she hit her head against a wall about nine months later. Presented to her local A&E 2 months after her first injury, and a plain skull X-ray was done - ? cosmetic reasons and pain over right frontal swelling. A prominent and abnormal area of radiolucency projected in the right frontal bone measuring approximately 5.5cm in maximum diameter was noted.
3. Hit head again during an altercation with boyfriend At the time of the second injury, she was about 7 months pregnant. Subsequently, the swelling started to increase progressively in size, and as at the time of admission, had increased to about 7.5 x 6cm. At second A&E visit, presented with a 24 hour history of nausea, vomiting and headaches. Clinical examination revealed dull pain over the frontal swelling. There was no neurological deficit. No papilloedema on fundoscopy.
4. Bloods - Hb 11.7 - Na 144 - WBC 6.6 - K 4.0 - Platelets 264 - ALT 18 - INR 1.0 - Alk Phos 526↑↑ - CRP <5 Bone profile – not done
5. Macroscopic description Portion of skull bone with diameter measuring 100 x 110mm. the skull bone is 8mm in thickness. The outer surface shows a vesicular 16mm defect and appears to be protruded through by an internal tumour which measures 60 x 60mm. On slicing, the tumour appears to infiltrate through the skull bone and measures up to 60mm in maximum thickness. Tumour shows a fleshy soft appearance and is associated with areas of necrosis.
6. Histology Bone forming tumour which is composed of islands of small trabeculae of osteoid all of which are surrounded by a rim of osteoblasts and they contain trapped osteocytes. Intervening loose fibrovascular stroma with numerous scattered osteoclasts. Focal ossification is seen. The mass is highly cellular and the cells seen show a degree of cellular and nuclear atypia together with focal epitheloid change. Frequent mitotic figures are seen although atypical mitosis is not a prominent feature.
7. Mitotic figures are conspicuous both in the osteoblast and mesenchymal population as well as in occasional endothelial cells. The edges of the mass seem rather well demarcated radiologically but focal histological permeation is seen. Throughout, there is marked vascular ectasia and haemorrhage. In conclusion, the lack of atypical mitosis and only focal permeation favours a diagnosis of an aggressive osteoblastoma with aneurysmal bone cyst-like change.
9. Introduction Osteoblastomas account for approximately 1% of all bone tumours Skull lesions have been sporadically described and account for 2.3 to 20% of all cases. Figuerido, Vellutini, Velasco et al Arq Neuropsiquiatr 1998; 56(2): 292-295 quoted only 35 cases reported in literature. Malignant osteoblastoma or aggressive osteoblastoma, are terms used to describe lesions that show atypical cytological features and may be correlated with recurrence. Associated aneurysmal bone cysts may be seen with as many as 10% of osteoblastomas.
10. History Initially reported by Jaffe and Mayer in 1932 Various names – “osteogenic fibroma of bone”, “giant osteoma osteoid” etc. The current term was proposed by Jaffe and Lichtenstein in 1956. Jaffe and Lichtenstein also coined the term “Aneurysmal bone cyst” in 1942 – to describe a peculiar bone lesion with a vascular lining and a characteristic soap bubble radiologic picture of expanded bone.
11. Epidemiology Males are affected more often than females (with an incidence of 2–3 : 1) Average age of occurrence is 17 years, ranging from 4 to 78 years. No racial predilection is recognised for cases of osteoblastoma
12. Sites Can affect every bone in the body Most frequently affected sites are – vertebrae, femur, jaw bones and tibia. Most common calvarial site – temporal region Other sites – clival, frontal & occipital A Rare Location of Benign Osteoblastoma: Review of the Literature and Report of a Case Bilkay, Ufuk MD; Erdem, Ozgur MD; Ozek, Cuneyt MD; Helvaci et al Journal of Craniofacial Surgery: March 2004 – Vol. 15 - Issue 2 (pp 222-225) Reported the 54th case of mandibular osteoblastomas
13. Classification Musculoskeletal Society Tumour Staging (MSTS) system of benign bone tumours Stage I tumours are asymptomatic and are usually discovered incidentally. They reach a stage of non-growth after a period of slow growth. Stage II lesions are characterized by benign cytologic characteristics, remain intracapsular, and do not metastasize. Most osteoblastomas are stage II lesions. Stage III osteoblastomas destroy bone much more aggressively and extend extracapsularly, the histologic architecture and cell structure remain benign.
14. Clinical features Progressive local pain is the most frequent clinical presentation The primary symptom is pain, and patients often characterize it as “dull and achy”. Unlike the pain of osteoid osteoma, the pain of osteoblastoma is more generalized, and less likely to be relieved by NSAIDS. Local swelling – average size reported in literature is 3.1cm Average duration of above 2 symptoms has been reported as 2 years. Hearing loss (temporal osteoblastomas) Features of raised intracranial pressure
15. Malignant transformation Malignant transformation of an osteoblastoma of the skull: an exceptional occurrenceDominique Figarella-Branger, M.D., Miguelina Perez-Castillo, M.D. et al Journal of Neurosurgery 1991.75.1.0138 - The initial lesion was completely removed surgically and showed the histological features typical of a benign osteoblastoma. - No radiotherapy was performed. - 11 years later the patient developed an osteosarcoma of the skull. Review of the literature showed that malignant transformation is extremely rare and could take place spontaneously. - Risk seems higher after inadequate initial treatment (curettage or partial excision).
16. Management Conservative – if small in size Surgical resection – Total removal is the aim of treatment. Recurrence has been reported in incomplete curettage of the lesion. This can be very difficult, especially in large tumours, because of the tendency to bleed intra-operatively. Embolisation Depending on location and arterial supply. Tom et al reported a 1350ml blood loss during the biopsy of a maxillary osteoblastoma. Tom LWC, Lowry LD & Quinn-Bogard A. Benign Osteoblastoma of the ethmoid sinus. Otolaryngol Head Neck Surg 1980;88:397-402 Radiotherapy Follow-up
17. Differential diagnoses Osteoid osteoma – usually affects the bony cortex and has a sclerotic nidus. It also has a smaller size at presentation, probably because pain is worse. Osteogenic sarcoma – very difficult to differentiate from aggressive osteoblastomas. Chondrosarcoma Benign giant cell tumour Fibrosarcoma
20. References Osteoblastoma of the Temporal Bone: CT findings. Fouad E. Gellad, Mohammed A. Hafiz and Cyrus L. Blanchard. Journal of Computer Assisted Tomography May/June 1985 9(3);577-579 Giant osteoblastoma of temporal bone. EbervalFiguierido, Eduardo Vellutini, Octavio Velasco and Patricia Bougar. Arq Neuopsiquiatr 1998;56(2):292-295 Classical osteoblastoma, atypical osteoblastoma and osteosarcoma: a comparative study based on clinical, histological and biological parameters. De Oliviera CR, Mendonca BB, de Camargo OP et al Clinics Apr 2007;62(2):167-74 Borderline osteoblastic tumours: problems in the differential diagnosis of aggressive osteoblastoma and low grade osteosarcoma.Dorfman HD, Weiss SW et al SeminDiagnpathol. 1984;1:215-34 Tumours and tumour-like lesions of bone: imaging and pathology of specific lesions. Resnick D. Diagnosis of Bone and Joint Disorders. 3rded Philadelphia, Pa:WB Saunders Co; 1995:3647-57 Benign osteoblastoma of the temporal bone. MotoomiOhkawa, Naomi Fujiwara, Masatada Tanabe et al AJNR 18:324-326, Feb 1997 Osteoblastoma: Varied Histological Presentations with a Benign Clinical Course – Analysis of 55 cases. Rocca, Carlo Della M.D, Huvos, Andrew G M.D The American Journal of Surgical Pathology Vol 20(7), July 1996, pp 841 – 850 Benign osteoblastoma of the temporal bone. Charles Potter, George H. Conner and Francis Sharkley. The American Journal of Otology April 1983 Vol 4, Number 4
