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Bizarre parosteal osteochondromatous proliferation of the foot
The Foor C1994) 4.92-94
Bizarre parosteal osteochondromatous proliferation of the foot C. A. J. Romanowski, D. M. McKenna, N. A. Barrington Department ofRadiology, Royal Hallamshire Hospital, Sheffield, UK, and Department of Pathology, University of Shefield Medical School, Shefield, UK
S UMMA R Y. Bizarre parosteal osteochondromatous proliferations (BPOPs) are rare tumours that occur in the hands and feet. There is a marked tendency towards local recurrence but the lesions do not metastasize or give rise to systemic effects. The radiological and pathological features of a typical BPOP of the foot are presented. The differential diagnosis for these lesions is discussed.
CASE REPORT
proximal phalanges and metacarpals and metatarsals. None have been described occurring with the terminal phalanges and this therefore distinguishes them from subungual exostoses.’ 35 of the 37 cases were reported by Nora et al’ who first introduced the term BPOP. The age range of their patients was 14-74 years (median 34 years) with 16 females and 19 males. None of their cases gave an antecedent history of trauma although in the other 2 reported cases there was such a history. Our patient did not recall a specific incident although it may be of note that his occupation as a trackman on the railways required him to be on his feet all day. Most patients complain of a lump in the soft tissues with limited joint movement. Pain is not a common feature and was not present in our patient. There is a marked tendency towards recurrence with 18 out of 35 of Nora’s cases recurring once and 8 of these recurring a second time. The long-term recurrence rate may be even higher than this. The lesions do not however metastasize or give rise to systemic effects, nor have they caused any deaths. Radiological BPOPs are well defined, calcified, pedunculated or sessile tumours up to 3.0 cm in diameter. They arise directly from the bone cortex but do not alter or destroy it, nor do they cause a periosteal reaction. Pathologically, they have a smooth lobulated surface and consist of bone covered by an irregular cartilaginous cap. Histologically, the interface between the cartilage cap and the underlying bone is very irregular and resembles fracture callus containing many plump, even atypical chondrocytes. Intervening fibrous tissue is characteristically highly cellular but lacks the nuclear atypia of sarcomatous lesions.4 The differential diagnosis for these lesions would include osteochondromas, ossifying haematomas,
A 49-year-old trackman working on the railways presented with a lump under his left middle toe. He had noticed this 6 weeks earlier and it had not grown any larger during that period. It was not painful unless he knocked it. There were no other local symptoms and he was generally well with no relevant past history. On examination, the only positive finding was a firm bony swelling adjacent to the proximal phalanx of the left middle toe. Plain radiographs showed a well defined, rather fluffy calcified mass related to the plantar aspect of the proximal phalanx (Fig. 1A). The cortex of the adjacent phalanx was intact and there was no evidence of periosteal reaction (Fig. 1B). In view of the initially worrying radiology the toe was amputated. The gross pathological examination of the lesion revealed a lobulated bony and cartilaginous white mass around the proximal phalanx. Histologically, this was composed of a disorganized osteocartilaginous neoplasm in which the dominant component was bone trabeculae mostly woven in type, resembling fracture callus in many areas. Irregular foci of cartilage containing plump chondrocytes were bordered by fibroblastic tissue showing increased cellularity (Fig. 2). Abnormal mitotic figures were not a feature of any of the tissue elements.
DISCUSSION Bizarre parosteal osteochondromatous proliferations (BPOPs) are rare tumours that occur in the hands and feet. Only 37 cases have been previously reported.le3 They occur adjacent to the middle and 92
Bizarre
Fig. l-(A) AP and (B) oblique middle toe.
Fig. 2-Histology section showing increased cellularity (arrow head).
views of the left foot showing
irregular
foci of cartilage
oarosteal
the BPOP related
with plump
osteochondromatous
to the plantar
chondrocytes
(arrow)
nroliferation
aspect of the proximal
bordered
by fibroblastic
of the foot
phalanx
of the
tissue showing
93
94 The Foot
parosteal osteosarcomas, chondrosarcomas and florid reactive periostitis. They can however be distinguished from these lesions on radiological and/or pathological grounds. Osteochondromas are different in that the centre of the lesion continues into the medullary cavity of the underlying bone of which the cortex is flared and merges with that of the osteochondroma. In BPOPs the cortex remains intact and does not flare out. Ossifying haematomas occur on the dorsal aspects of the proximal and middle phalanges after trivial trauma and are smaller than BPOPs. Parosteal osteosarcomas are exceedingly rare in the small bones of the hands or feet; only 1 case involving a metacarpal having been reported.’ These can be differentiated from from BPOPs histologically, the osteosarcomas showing fibrocytic atypia not seen in BPOPs. Florid reactive periostitis is a reaction to trauma with mature or laminated periosteal reaction, periosteal elevation and soft tissue swelling with juxtacortical calcification. BPOPs do not show any evidence of periosteal reaction. Chondrosarcomas are differentiated from BPOPs on histological appearances based on assessment of marked chondrocyte nuclear atypia and taking into consideration the rarity of such lesions in the small bones of the hands and feet. In conclusion, BPOPs are rare tumours of the hands or feet that although showing no evidence of metastasis do have a high incidence of local recurrence. They may be confused with certain other lesions such as osteochondromas, ossifying haematomas, parosteal osteosarcomas, chondrosarcomas and florid reactive periostitis. The differentiation however can be made by combined radiological and histological appearances.
Acknowledgements We would like to thank Mr D. Surgeon, Royal Hallamshire this case and Dr L. Harvey, District General Hospital for
L. Douglas, Consultant Orthopaedic Hospital, for permission to publish Consultant Pathologist, Rotherham his valued opinion on this case.
References 1. Nora F E, Dahlin D C, Beabout J W. Bizarre parosteal osteochondromatous proliferations of the hands and feet. Am J Surg Path01 1983; 7: 245-250. 2. Davies C W T. Bizarre parosteal osteochondromatous proliferation in the hand. J Bone Joint Surg 1985; 67A: 648-650. 3. de Lange E E, Pope T L Jr, Fechner R E, Keats T E. Bizarre parosteal osteochondromatous proliferation. Case report 428. Skeletal Radio1 1987, 16: 481483. 4. Reid R P, Catto M E. Some unusual tumours of cartilage and pseudosarcoma of the hand. In: Anthony P P, MacSween R N M, eds. Recent advances in histopathology No. 13. Edinburgh: Churchill Livingstone, 1987: 74-76. 5. Stark H H, Jones F E, Jemstrom P. Parosteal osteogenic sarcoma of a metacarpal bone. J Bone Joint Surg 1971; 53A: 147-153.
The authors C. A. J. Romanowski N. A. Barrington Department of Radiology Royal Hallamshire Hospital Sheffield SlO 2JF UK D. M. McKenna Department of Pathology University of Sheffield Medical School Sheffield UK Correspondence to Dr C. A. J. Romanowski.
Bizarre parosteal osteochondromatous proliferation of the foot C. A. J. Romanowski, D. M. McKenna, N. A. Barrington Department ofRadiology, Royal Hallamshire Hospital, Sheffield, UK, and Department of Pathology, University of Shefield Medical School, Shefield, UK
S UMMA R Y. Bizarre parosteal osteochondromatous proliferations (BPOPs) are rare tumours that occur in the hands and feet. There is a marked tendency towards local recurrence but the lesions do not metastasize or give rise to systemic effects. The radiological and pathological features of a typical BPOP of the foot are presented. The differential diagnosis for these lesions is discussed.
CASE REPORT
proximal phalanges and metacarpals and metatarsals. None have been described occurring with the terminal phalanges and this therefore distinguishes them from subungual exostoses.’ 35 of the 37 cases were reported by Nora et al’ who first introduced the term BPOP. The age range of their patients was 14-74 years (median 34 years) with 16 females and 19 males. None of their cases gave an antecedent history of trauma although in the other 2 reported cases there was such a history. Our patient did not recall a specific incident although it may be of note that his occupation as a trackman on the railways required him to be on his feet all day. Most patients complain of a lump in the soft tissues with limited joint movement. Pain is not a common feature and was not present in our patient. There is a marked tendency towards recurrence with 18 out of 35 of Nora’s cases recurring once and 8 of these recurring a second time. The long-term recurrence rate may be even higher than this. The lesions do not however metastasize or give rise to systemic effects, nor have they caused any deaths. Radiological BPOPs are well defined, calcified, pedunculated or sessile tumours up to 3.0 cm in diameter. They arise directly from the bone cortex but do not alter or destroy it, nor do they cause a periosteal reaction. Pathologically, they have a smooth lobulated surface and consist of bone covered by an irregular cartilaginous cap. Histologically, the interface between the cartilage cap and the underlying bone is very irregular and resembles fracture callus containing many plump, even atypical chondrocytes. Intervening fibrous tissue is characteristically highly cellular but lacks the nuclear atypia of sarcomatous lesions.4 The differential diagnosis for these lesions would include osteochondromas, ossifying haematomas,
A 49-year-old trackman working on the railways presented with a lump under his left middle toe. He had noticed this 6 weeks earlier and it had not grown any larger during that period. It was not painful unless he knocked it. There were no other local symptoms and he was generally well with no relevant past history. On examination, the only positive finding was a firm bony swelling adjacent to the proximal phalanx of the left middle toe. Plain radiographs showed a well defined, rather fluffy calcified mass related to the plantar aspect of the proximal phalanx (Fig. 1A). The cortex of the adjacent phalanx was intact and there was no evidence of periosteal reaction (Fig. 1B). In view of the initially worrying radiology the toe was amputated. The gross pathological examination of the lesion revealed a lobulated bony and cartilaginous white mass around the proximal phalanx. Histologically, this was composed of a disorganized osteocartilaginous neoplasm in which the dominant component was bone trabeculae mostly woven in type, resembling fracture callus in many areas. Irregular foci of cartilage containing plump chondrocytes were bordered by fibroblastic tissue showing increased cellularity (Fig. 2). Abnormal mitotic figures were not a feature of any of the tissue elements.
DISCUSSION Bizarre parosteal osteochondromatous proliferations (BPOPs) are rare tumours that occur in the hands and feet. Only 37 cases have been previously reported.le3 They occur adjacent to the middle and 92
Bizarre
Fig. l-(A) AP and (B) oblique middle toe.
Fig. 2-Histology section showing increased cellularity (arrow head).
views of the left foot showing
irregular
foci of cartilage
oarosteal
the BPOP related
with plump
osteochondromatous
to the plantar
chondrocytes
(arrow)
nroliferation
aspect of the proximal
bordered
by fibroblastic
of the foot
phalanx
of the
tissue showing
93
94 The Foot
parosteal osteosarcomas, chondrosarcomas and florid reactive periostitis. They can however be distinguished from these lesions on radiological and/or pathological grounds. Osteochondromas are different in that the centre of the lesion continues into the medullary cavity of the underlying bone of which the cortex is flared and merges with that of the osteochondroma. In BPOPs the cortex remains intact and does not flare out. Ossifying haematomas occur on the dorsal aspects of the proximal and middle phalanges after trivial trauma and are smaller than BPOPs. Parosteal osteosarcomas are exceedingly rare in the small bones of the hands or feet; only 1 case involving a metacarpal having been reported.’ These can be differentiated from from BPOPs histologically, the osteosarcomas showing fibrocytic atypia not seen in BPOPs. Florid reactive periostitis is a reaction to trauma with mature or laminated periosteal reaction, periosteal elevation and soft tissue swelling with juxtacortical calcification. BPOPs do not show any evidence of periosteal reaction. Chondrosarcomas are differentiated from BPOPs on histological appearances based on assessment of marked chondrocyte nuclear atypia and taking into consideration the rarity of such lesions in the small bones of the hands and feet. In conclusion, BPOPs are rare tumours of the hands or feet that although showing no evidence of metastasis do have a high incidence of local recurrence. They may be confused with certain other lesions such as osteochondromas, ossifying haematomas, parosteal osteosarcomas, chondrosarcomas and florid reactive periostitis. The differentiation however can be made by combined radiological and histological appearances.
Acknowledgements We would like to thank Mr D. Surgeon, Royal Hallamshire this case and Dr L. Harvey, District General Hospital for
L. Douglas, Consultant Orthopaedic Hospital, for permission to publish Consultant Pathologist, Rotherham his valued opinion on this case.
References 1. Nora F E, Dahlin D C, Beabout J W. Bizarre parosteal osteochondromatous proliferations of the hands and feet. Am J Surg Path01 1983; 7: 245-250. 2. Davies C W T. Bizarre parosteal osteochondromatous proliferation in the hand. J Bone Joint Surg 1985; 67A: 648-650. 3. de Lange E E, Pope T L Jr, Fechner R E, Keats T E. Bizarre parosteal osteochondromatous proliferation. Case report 428. Skeletal Radio1 1987, 16: 481483. 4. Reid R P, Catto M E. Some unusual tumours of cartilage and pseudosarcoma of the hand. In: Anthony P P, MacSween R N M, eds. Recent advances in histopathology No. 13. Edinburgh: Churchill Livingstone, 1987: 74-76. 5. Stark H H, Jones F E, Jemstrom P. Parosteal osteogenic sarcoma of a metacarpal bone. J Bone Joint Surg 1971; 53A: 147-153.
The authors C. A. J. Romanowski N. A. Barrington Department of Radiology Royal Hallamshire Hospital Sheffield SlO 2JF UK D. M. McKenna Department of Pathology University of Sheffield Medical School Sheffield UK Correspondence to Dr C. A. J. Romanowski.