Skeletal Radiol (1991) 20:1~4
Skeletal Radiology
Recurring osteoblastoma initially presenting as a typical osteoid osteoma* Report o f t w o c a s e s G. Bettelli, M.D., D. Tigani, M.D. and P. Picci, M.D. Bone Tumor Center, Istituto Ortopedico Rizzoli, Bologna, Italy
Abstract. Two p a t i e n t s e a c h u n d e r w e n t i n a d e q u a t e excision o f a n o s t e o i d o s t e o m a a n d s o m e m o n t h s l a t e r d e v e l o p e d a large t u m o r in the s a m e l o c a t i o n s h o w i n g the r a d i o g r a p h i c a l a n d h i s t o l o g i c a l f e a t u r e s o f o s t e o b l a s t o m a . This r a r e o c c u r r e n c e a g a i n suggests t h a t o s t e o i d o s t e o m a a n d o s t e o b l a s t o m a a r e closely c o n n e c t e d benign n e o p l a s m s . I n d e e d s o m e a u t h o r s in the p a s t h a v e s u g g e s t e d c l a s s i f i c a t i o n as a single t u m o r s h o w i n g different clinical a n d r a d i o g r a p h i c a l p a t t e r n s . Key words: O s t e o i d o s t e o m a
Osteoblastoma
Osteoid osteoma and osteoblastoma are benign osteoblastic t u m o r s w i t h closely similar h i s t o l o g i c aspects [2, 3, 7, 13]. T h e y are c o n s i d e r e d s e p a r a t e entities o n acc o u n t o f their skeletal d i s t r i b u t i o n a n d r a d i o g r a p h i c a n d clinical pictures. T h e m a i n distinctive f a c t o r is size, as o s t e o i d o s t e o m a s h o w s v e r y limited g r o w t h a n d n e v e r exceeds 1 - 2 c m in d i a m e t e r , w h e r e a s o s t e o b l a s t o m a c a n b e c o m e a large t u m o r . S o m e cases are e n c o u n t e r e d , h o w e v e r , in w h i c h b o r derline size a n d clinical a n d h i s t o l o g i c a l aspects m a k e it i m p o s s i b l e to define to w h i c h g r o u p the lesion belongs. Such cases a r e s o m e t i m e s r e f e r r e d to as " g i a n t o s t e o i d o s t e o m a s " [4]. T h e existence o f these b o r d e r l i n e f o r m s , t o g e t h e r w i t h the o v e r l a p p i n g h i s t o l o g i c a l a p p e a r a n c e s , has p r o m p t e d m a n y a u t h o r s to suggest t h a t o s t e o i d ost e o m a a n d o s t e o b l a s t o m a m a y be different a s p e c t s o f one t u m o r [5, 16]. Address reprint requests to: Graziano Bettelli, Clinica Ortopedica 1~ Istituto Ortopedico Rizzoli, 40136 Bologna, Italy * Supported by: Grant n ~ 88.01124.44, Italian National Council of Researches, Special Project "Oncology". A.I.R.C. (Italian Association for Cancer Research). Regione Emilia-Romagna, law n ~ 1970 of May 13th, 1986. Istituto Ortopedico Rizzoli Research Funds. Interdepartmental Center for Cancer Research "G. Prodi" of the University of Bologna
We r e p o r t two cases in w h i c h after excision o f a tum o r w i t h the features o f o s t e o i d o s t e o m a a r e c u r r e n c e developed showing a pattern typical of osteoblastoma.
Case reports Case 1 A.B., a 24-year-old woman, began to suffer pain in her right thigh without any history of trauma. Pain increased and was reduced by nonsteroidal anti-inflammatory drugs. After 9 months, as symptoms were worsening, she was admitted to hospital; plain films and tomograms showed a small osteolytic area, about 6 mm in diameter, on the surface of the medial cortex of the femur, surrounded by a large amount of reactive bone (Fig. 1). She underwent excision and multiple drilling (Fig. 2) of the tumor. The histological diagnosis was osteoid osteoma (Fig. 3). Eight months later, symptoms recurred. New radiographs showed a dense lesion occupying about 10 cm of the mid-third of the femur with three distinct lytic areas each about 2-3 cm in diameter (Fig. 4). The isotope scan was markedly positive. Magnetic resonance imaging (MRI) scan was also obtained (Fig. 5). The patient was admitted to our service, and a diaphyseal resection and reconstruction with autografts and a screwed nail were performed after a biopsy which gave the histological diagnosis of osteoblastoma (Fig. 6). Case 2 G.A., an 18-year-old man, had been suffering pain in his left groin for 6 months when he was admitted to hospital Radiographs showed a small lytic area, about 10 mm in diameter, in the medial cortex of the neck of the femur (Fig. 7). A clinical and radiologic diagnosis of osteoid osteoma was made. The pain did not disappear completely after excision, and no tumor could be found in the surgical specimen. After 14 months he entered our department complaining of pain in his left hip. The hip motion was impaired, and a mass could be appreciated in the groin on physical examination. Radiographs (Fig. 8) showed a large lyric tumor occupying the neck of the femur. Invasion of the soft tissues was evident from computed tomography (CT) scan and MR image (Fig. 9). A wide resection of the proximal femur and implant of a Kotz modular prosthesis was performed. After histological examination of the whole specimen a diagnosis of osteoblastoma was established (Fig. 10). 9 1991 International Skeletal Society
2
Fig. 1. Case 1. AP view of diaphysis of femur, showing a large amount of reactive bone with a small radiolucency on the surface of the medial cortex Fig. 2. A radiograph taken after the operation shows the holes made by drilling the lesion Fig. 3. Histologic appearance of part of the nidus, Note the osteoblasts forming osteoid trabeculae and the presence of numerous small vessels. Osteoclasts are also remodelling the newly formed bone. (H & E, x 200 original magnification) Fig. 4A, B. AP and lateral radiograph of the same femur 8 months after excision of the osteoid osteoma show a large recnrring tumor
G. Bettelli et al. : Recurring osteoblastoma
G. Bettelli et al. : Recurring osteoblastoma
3
Fig. 7. Case 2. A small lytic area is present in the medial cortex of the neck of the femur in an 18-yearold man. The lesion had been painful for 6 months when this radiograph was taken Fig. 8. One year after an attempt at surgical excision, the tumor had attained a considerable size, extensively invading the neck of the femur Fig. 5. Magnetic resonance image demonstrates three separate foci of recurring tumor Fig. 6. Histologic aspect of the recurrent lesion, diagnosed as osteoblastoma. Tumor lacks the organoid aspect of osteoid osteoma but shows the same cellular components of the former lesion. (H & E, x 100 original magnification)
Discussion O s t e o b l a s t o m a was first d e s c r i b e d as a s e p a r a t e n e o p l a s m in 1956 b y Jaffe [9] a n d L i c h t e n s t e i n [10], w h o i n d e p e n d e n t l y chose this n a m e to i d e n t i f y b e n i g n o s t e o b l a s t i c t u m o r s w i t h r a d i o g r a p h i c a l a n d clinical aspects different f r o m o s t e o i d o s t e o m a . B o r d e r l i n e cases, h o w ever, exist w h e n h i s t o l o g i c a l f e a t u r e s d o n o t a l l o w a definitive d i s t i n c t i o n b e t w e e n o s t e o i d o s t e o m a a n d o s t e o b l a s t o m a . In fact in 1954 D a h l i n a n d J o h n s o n [4] described 11 o s t e o b l a s t i c t u m o r s u n d e r the d e f i n i t i o n o f " g i a n t o s t e o i d o s t e o m a s , " stressing the c o m m o n histological aspects. Two tendencies a r e m e t in the l i t e r a t u r e c o n c e r n i n g
Fig. 9. Tumor extension shown on magnetic resonance image Fig. 10. Histological appearance is consistent with both osteoid osteoma and osteoblastoma so that a definite diagnosis on a single histological field cannot be given. Note the reactive bone surrounding this small nodule. (H & E, x 200 original magnification)
the classification o f these t u m o r s . T h e first is to r e t a i n a sharp distinction between osteoid osteoma and osteob l a s t o m a , using the size as a conclusive c r i t e r i o n in d o u b t f u l cases. This o p i n i o n is s h a r e d b y m o s t a u t h o r s , a n d a d i a m e t e r o f 1.5 c m [12] o r 2 c m [7, 13] is c o n s i d e r e d as the " b r e a k i n g p o i n t . " T h e o t h e r o r i e n t a t i o n is to c o n s i d e r o s t e o i d o s t e o m a a n d o s t e o b l a s t o m a as a single n o s o l o g i c a l e n t i t y t h a t c a n d e v e l o p in v a r i o u s ways. T h o s e w h o s u p p o r t this p o i n t o f view suggest s u b s t i t u t ing the t e r m o s t e o i d o s t e o m a w i t h " c i r c u m s c r i b e d ost e o b l a s t o m a " [14, 16] o r to m a k e a d i s t i n c t i o n b e t w e e n "cortical," "spongious," and "periosteal" osteoblastom a s [5]. T h e cases r e p o r t e d here seem to s u p p o r t the l a t t e r
4 opinion. In a review of the literature we were able to find only two cases in which an osteoid osteoma was inadequately excised (so that there was histological confirmation of the diagnosis), and the recurring t u m o r had the size and appearance typical of osteoblastoma [15, 16]. Other impressive observations deal with cases of typical osteoid osteoma that were not treated and grew in size, attaining the features of an osteoblastoma [I,
G. Bettelli et al. : Recurring osteoblastoma must always be treated by complete excision. I f this rule is not respected, the patient runs the risk of a recurrence that can cause, in some cases, far greater therapeutic problems than the small original tumor. In one of our cases in fact the recurrence presented in three different foci, probably following dissemination of the original osteoid osteoma by multiple drilling.
181. One can therefore state the hypothesis that all these neoplasms pass through an initial stage with radiological appearances of osteoid osteoma and then evolve to the picture of osteoblastoma; the persistence of a characteristic osteoid osteoma might be due to an unpredictable balance between the growth potential of the lesion and the capacity of bone to control the t u m o r by production of reactive tissue. We think, however, that the observations of " t r a n s i t i o n a l " forms are too rare to confirm such a possibility. Some authors [5, 8] have suggested that the different evolution of the t u m o r to osteoid osteoma or osteoblastoma could relate to the quality of the host bone. The medullary bone could be less efficient in containing the development of this neoplasm than the cortical bone. This idea is undoubtedly attractive and would be supported by the different skeletal distribution (higher frequency o f osteoid osteoma in the long tubular bones of the limbs and of osteoblastoma in the spine and short bones), but it cannot explain the existence of typical osteoid osteomas that originate in spongiosa (e.g., within the body of the talus) and still do not change their appearance even if not treated for long periods. R is noteworthy, moreover, that histological studies demonstrate a higher concentration of nerve fibers in osteoid osteoma than in osteoblastoma [17] and that the former is characterized by prostaglandin secretion [6, 11]. These studies support the opinion that the two entities are truly different. In conclusion, we do not believe that it would be useful in practice to reject the nosological distinction between osteoid osteoma and osteoblastoma, especially since its application is entirely feasible in the vast majority of cases. On the other hand, the occurrence of unusual cases such as those reported here, stresses the close relation between these osteoblastic tumors and offers an additional reason to remember that osteoid osteoma
References 1. Byers PD (1968) Solitary benign osteoblastic lesions of bone. Osteoid osteoma and benign osteoblastoma. Cancer 22:43 2. Campanaeci M (1981) Tumori delle ossa e delle parti molli. Aulo Gaggi Editore, Bologna, p 289 3. Dahlin DC (1978) Bone tumors. General aspects and data on 6,221 cases. C.C. Thomas, Springfield, p 75 4. Dahlin DC, Johnson EW (1954) Giant osteoid osteoma. J Bone Joint Surg [Am] 36(3):559 5. De Souza Dias L, Frost HM (1974) Osteoid osteoma - osteoblastoma. Cancer 33 : 1075 6. Healey JH, Ghelman B (1986) Osteoid osteoma and osteoblastoma. Current concepts and recent advances. Clin Orthop 204:76 7. Huvos AG (1979) Bone tumors. Diagnosis, treatment and prognosis. W.B. Saunders, Philadelphia, p 18 8. Jackson RP, Reckling FW, Mantz FA (1977) Osteoid osteoma and osteoblastoma. Similar histologic lesions with different natural histories. Clin Orthop 128:303 9. Jaffe HL (1956) Benign osteoblastoma. Bull Hosp Joint Dis 17:141 10. Lichtenstein L (1956) Benign osteoblastoma. Cancer 9:1044 11. Makely J (1982) Prostaglandins: a mechanism for pain mediation in osteoid osteoma. Orthop Trans 6:72 12. McLeod RA, Dahlin DC, Beabout JW (1976) The spectrum of osteoblastoma. Am J Roentgenol 126:321 13. Mirra JM (1980) Bone tumors. Diagnosis and treatment. J.B. Lippincott, Philadelphia, p 97 14. Morton KS, Vassar PS, Knickerbocker WJ (1975) Osteoid osteoma and osteoblastoma: reclassification of 43 cases using Schajowicz's classification. Can J Surg 18:148 15. Morton KS, Quenville NF, Beauehamp CP (1989) Aggressive osteoblastoma. A case previously reported as a recurrent osteoid osteoma. J Bone Joint Surg [Br] 71:428 16. Schajowicz F, Lemos C (1970) Osteoid osteoma and osteoblastoma. Closely related entities of osteoblastic derivation. Acta Orthop Scand 41 : 272 17. Schulman L, Dorfman HD (1970) Nerve fibers in osteoid osteoma. J Bone Joint Surg [Am] 52:1351 18. Wilner D (1982) Radiology of bone tumors and allied disorders. W.B. Saunders, Philadelphia, p 144
Skeletal Radiology
Recurring osteoblastoma initially presenting as a typical osteoid osteoma* Report o f t w o c a s e s G. Bettelli, M.D., D. Tigani, M.D. and P. Picci, M.D. Bone Tumor Center, Istituto Ortopedico Rizzoli, Bologna, Italy
Abstract. Two p a t i e n t s e a c h u n d e r w e n t i n a d e q u a t e excision o f a n o s t e o i d o s t e o m a a n d s o m e m o n t h s l a t e r d e v e l o p e d a large t u m o r in the s a m e l o c a t i o n s h o w i n g the r a d i o g r a p h i c a l a n d h i s t o l o g i c a l f e a t u r e s o f o s t e o b l a s t o m a . This r a r e o c c u r r e n c e a g a i n suggests t h a t o s t e o i d o s t e o m a a n d o s t e o b l a s t o m a a r e closely c o n n e c t e d benign n e o p l a s m s . I n d e e d s o m e a u t h o r s in the p a s t h a v e s u g g e s t e d c l a s s i f i c a t i o n as a single t u m o r s h o w i n g different clinical a n d r a d i o g r a p h i c a l p a t t e r n s . Key words: O s t e o i d o s t e o m a
Osteoblastoma
Osteoid osteoma and osteoblastoma are benign osteoblastic t u m o r s w i t h closely similar h i s t o l o g i c aspects [2, 3, 7, 13]. T h e y are c o n s i d e r e d s e p a r a t e entities o n acc o u n t o f their skeletal d i s t r i b u t i o n a n d r a d i o g r a p h i c a n d clinical pictures. T h e m a i n distinctive f a c t o r is size, as o s t e o i d o s t e o m a s h o w s v e r y limited g r o w t h a n d n e v e r exceeds 1 - 2 c m in d i a m e t e r , w h e r e a s o s t e o b l a s t o m a c a n b e c o m e a large t u m o r . S o m e cases are e n c o u n t e r e d , h o w e v e r , in w h i c h b o r derline size a n d clinical a n d h i s t o l o g i c a l aspects m a k e it i m p o s s i b l e to define to w h i c h g r o u p the lesion belongs. Such cases a r e s o m e t i m e s r e f e r r e d to as " g i a n t o s t e o i d o s t e o m a s " [4]. T h e existence o f these b o r d e r l i n e f o r m s , t o g e t h e r w i t h the o v e r l a p p i n g h i s t o l o g i c a l a p p e a r a n c e s , has p r o m p t e d m a n y a u t h o r s to suggest t h a t o s t e o i d ost e o m a a n d o s t e o b l a s t o m a m a y be different a s p e c t s o f one t u m o r [5, 16]. Address reprint requests to: Graziano Bettelli, Clinica Ortopedica 1~ Istituto Ortopedico Rizzoli, 40136 Bologna, Italy * Supported by: Grant n ~ 88.01124.44, Italian National Council of Researches, Special Project "Oncology". A.I.R.C. (Italian Association for Cancer Research). Regione Emilia-Romagna, law n ~ 1970 of May 13th, 1986. Istituto Ortopedico Rizzoli Research Funds. Interdepartmental Center for Cancer Research "G. Prodi" of the University of Bologna
We r e p o r t two cases in w h i c h after excision o f a tum o r w i t h the features o f o s t e o i d o s t e o m a a r e c u r r e n c e developed showing a pattern typical of osteoblastoma.
Case reports Case 1 A.B., a 24-year-old woman, began to suffer pain in her right thigh without any history of trauma. Pain increased and was reduced by nonsteroidal anti-inflammatory drugs. After 9 months, as symptoms were worsening, she was admitted to hospital; plain films and tomograms showed a small osteolytic area, about 6 mm in diameter, on the surface of the medial cortex of the femur, surrounded by a large amount of reactive bone (Fig. 1). She underwent excision and multiple drilling (Fig. 2) of the tumor. The histological diagnosis was osteoid osteoma (Fig. 3). Eight months later, symptoms recurred. New radiographs showed a dense lesion occupying about 10 cm of the mid-third of the femur with three distinct lytic areas each about 2-3 cm in diameter (Fig. 4). The isotope scan was markedly positive. Magnetic resonance imaging (MRI) scan was also obtained (Fig. 5). The patient was admitted to our service, and a diaphyseal resection and reconstruction with autografts and a screwed nail were performed after a biopsy which gave the histological diagnosis of osteoblastoma (Fig. 6). Case 2 G.A., an 18-year-old man, had been suffering pain in his left groin for 6 months when he was admitted to hospital Radiographs showed a small lytic area, about 10 mm in diameter, in the medial cortex of the neck of the femur (Fig. 7). A clinical and radiologic diagnosis of osteoid osteoma was made. The pain did not disappear completely after excision, and no tumor could be found in the surgical specimen. After 14 months he entered our department complaining of pain in his left hip. The hip motion was impaired, and a mass could be appreciated in the groin on physical examination. Radiographs (Fig. 8) showed a large lyric tumor occupying the neck of the femur. Invasion of the soft tissues was evident from computed tomography (CT) scan and MR image (Fig. 9). A wide resection of the proximal femur and implant of a Kotz modular prosthesis was performed. After histological examination of the whole specimen a diagnosis of osteoblastoma was established (Fig. 10). 9 1991 International Skeletal Society
2
Fig. 1. Case 1. AP view of diaphysis of femur, showing a large amount of reactive bone with a small radiolucency on the surface of the medial cortex Fig. 2. A radiograph taken after the operation shows the holes made by drilling the lesion Fig. 3. Histologic appearance of part of the nidus, Note the osteoblasts forming osteoid trabeculae and the presence of numerous small vessels. Osteoclasts are also remodelling the newly formed bone. (H & E, x 200 original magnification) Fig. 4A, B. AP and lateral radiograph of the same femur 8 months after excision of the osteoid osteoma show a large recnrring tumor
G. Bettelli et al. : Recurring osteoblastoma
G. Bettelli et al. : Recurring osteoblastoma
3
Fig. 7. Case 2. A small lytic area is present in the medial cortex of the neck of the femur in an 18-yearold man. The lesion had been painful for 6 months when this radiograph was taken Fig. 8. One year after an attempt at surgical excision, the tumor had attained a considerable size, extensively invading the neck of the femur Fig. 5. Magnetic resonance image demonstrates three separate foci of recurring tumor Fig. 6. Histologic aspect of the recurrent lesion, diagnosed as osteoblastoma. Tumor lacks the organoid aspect of osteoid osteoma but shows the same cellular components of the former lesion. (H & E, x 100 original magnification)
Discussion O s t e o b l a s t o m a was first d e s c r i b e d as a s e p a r a t e n e o p l a s m in 1956 b y Jaffe [9] a n d L i c h t e n s t e i n [10], w h o i n d e p e n d e n t l y chose this n a m e to i d e n t i f y b e n i g n o s t e o b l a s t i c t u m o r s w i t h r a d i o g r a p h i c a l a n d clinical aspects different f r o m o s t e o i d o s t e o m a . B o r d e r l i n e cases, h o w ever, exist w h e n h i s t o l o g i c a l f e a t u r e s d o n o t a l l o w a definitive d i s t i n c t i o n b e t w e e n o s t e o i d o s t e o m a a n d o s t e o b l a s t o m a . In fact in 1954 D a h l i n a n d J o h n s o n [4] described 11 o s t e o b l a s t i c t u m o r s u n d e r the d e f i n i t i o n o f " g i a n t o s t e o i d o s t e o m a s , " stressing the c o m m o n histological aspects. Two tendencies a r e m e t in the l i t e r a t u r e c o n c e r n i n g
Fig. 9. Tumor extension shown on magnetic resonance image Fig. 10. Histological appearance is consistent with both osteoid osteoma and osteoblastoma so that a definite diagnosis on a single histological field cannot be given. Note the reactive bone surrounding this small nodule. (H & E, x 200 original magnification)
the classification o f these t u m o r s . T h e first is to r e t a i n a sharp distinction between osteoid osteoma and osteob l a s t o m a , using the size as a conclusive c r i t e r i o n in d o u b t f u l cases. This o p i n i o n is s h a r e d b y m o s t a u t h o r s , a n d a d i a m e t e r o f 1.5 c m [12] o r 2 c m [7, 13] is c o n s i d e r e d as the " b r e a k i n g p o i n t . " T h e o t h e r o r i e n t a t i o n is to c o n s i d e r o s t e o i d o s t e o m a a n d o s t e o b l a s t o m a as a single n o s o l o g i c a l e n t i t y t h a t c a n d e v e l o p in v a r i o u s ways. T h o s e w h o s u p p o r t this p o i n t o f view suggest s u b s t i t u t ing the t e r m o s t e o i d o s t e o m a w i t h " c i r c u m s c r i b e d ost e o b l a s t o m a " [14, 16] o r to m a k e a d i s t i n c t i o n b e t w e e n "cortical," "spongious," and "periosteal" osteoblastom a s [5]. T h e cases r e p o r t e d here seem to s u p p o r t the l a t t e r
4 opinion. In a review of the literature we were able to find only two cases in which an osteoid osteoma was inadequately excised (so that there was histological confirmation of the diagnosis), and the recurring t u m o r had the size and appearance typical of osteoblastoma [15, 16]. Other impressive observations deal with cases of typical osteoid osteoma that were not treated and grew in size, attaining the features of an osteoblastoma [I,
G. Bettelli et al. : Recurring osteoblastoma must always be treated by complete excision. I f this rule is not respected, the patient runs the risk of a recurrence that can cause, in some cases, far greater therapeutic problems than the small original tumor. In one of our cases in fact the recurrence presented in three different foci, probably following dissemination of the original osteoid osteoma by multiple drilling.
181. One can therefore state the hypothesis that all these neoplasms pass through an initial stage with radiological appearances of osteoid osteoma and then evolve to the picture of osteoblastoma; the persistence of a characteristic osteoid osteoma might be due to an unpredictable balance between the growth potential of the lesion and the capacity of bone to control the t u m o r by production of reactive tissue. We think, however, that the observations of " t r a n s i t i o n a l " forms are too rare to confirm such a possibility. Some authors [5, 8] have suggested that the different evolution of the t u m o r to osteoid osteoma or osteoblastoma could relate to the quality of the host bone. The medullary bone could be less efficient in containing the development of this neoplasm than the cortical bone. This idea is undoubtedly attractive and would be supported by the different skeletal distribution (higher frequency o f osteoid osteoma in the long tubular bones of the limbs and of osteoblastoma in the spine and short bones), but it cannot explain the existence of typical osteoid osteomas that originate in spongiosa (e.g., within the body of the talus) and still do not change their appearance even if not treated for long periods. R is noteworthy, moreover, that histological studies demonstrate a higher concentration of nerve fibers in osteoid osteoma than in osteoblastoma [17] and that the former is characterized by prostaglandin secretion [6, 11]. These studies support the opinion that the two entities are truly different. In conclusion, we do not believe that it would be useful in practice to reject the nosological distinction between osteoid osteoma and osteoblastoma, especially since its application is entirely feasible in the vast majority of cases. On the other hand, the occurrence of unusual cases such as those reported here, stresses the close relation between these osteoblastic tumors and offers an additional reason to remember that osteoid osteoma
References 1. Byers PD (1968) Solitary benign osteoblastic lesions of bone. Osteoid osteoma and benign osteoblastoma. Cancer 22:43 2. Campanaeci M (1981) Tumori delle ossa e delle parti molli. Aulo Gaggi Editore, Bologna, p 289 3. Dahlin DC (1978) Bone tumors. General aspects and data on 6,221 cases. C.C. Thomas, Springfield, p 75 4. Dahlin DC, Johnson EW (1954) Giant osteoid osteoma. J Bone Joint Surg [Am] 36(3):559 5. De Souza Dias L, Frost HM (1974) Osteoid osteoma - osteoblastoma. Cancer 33 : 1075 6. Healey JH, Ghelman B (1986) Osteoid osteoma and osteoblastoma. Current concepts and recent advances. Clin Orthop 204:76 7. Huvos AG (1979) Bone tumors. Diagnosis, treatment and prognosis. W.B. Saunders, Philadelphia, p 18 8. Jackson RP, Reckling FW, Mantz FA (1977) Osteoid osteoma and osteoblastoma. Similar histologic lesions with different natural histories. Clin Orthop 128:303 9. Jaffe HL (1956) Benign osteoblastoma. Bull Hosp Joint Dis 17:141 10. Lichtenstein L (1956) Benign osteoblastoma. Cancer 9:1044 11. Makely J (1982) Prostaglandins: a mechanism for pain mediation in osteoid osteoma. Orthop Trans 6:72 12. McLeod RA, Dahlin DC, Beabout JW (1976) The spectrum of osteoblastoma. Am J Roentgenol 126:321 13. Mirra JM (1980) Bone tumors. Diagnosis and treatment. J.B. Lippincott, Philadelphia, p 97 14. Morton KS, Vassar PS, Knickerbocker WJ (1975) Osteoid osteoma and osteoblastoma: reclassification of 43 cases using Schajowicz's classification. Can J Surg 18:148 15. Morton KS, Quenville NF, Beauehamp CP (1989) Aggressive osteoblastoma. A case previously reported as a recurrent osteoid osteoma. J Bone Joint Surg [Br] 71:428 16. Schajowicz F, Lemos C (1970) Osteoid osteoma and osteoblastoma. Closely related entities of osteoblastic derivation. Acta Orthop Scand 41 : 272 17. Schulman L, Dorfman HD (1970) Nerve fibers in osteoid osteoma. J Bone Joint Surg [Am] 52:1351 18. Wilner D (1982) Radiology of bone tumors and allied disorders. W.B. Saunders, Philadelphia, p 144
