Year : 2008 | Volume
: 51 | Issue : 4 | Page : 538--540
Polymorphic fibro-osseous lesion of the bone: A case report with review of literature
Anuradha C.K Rao1, Chennakeshav G Rao2,
1 Department of Pathology, Kasturba Medical College, Manipal, India
2 Department of Orthopedics, KVG Medical College, Sullia, India
Anuradha C.K Rao
Department of Pathology, Basic Sciences Block, II Floor, KMC, Manipal, Karnataka 576 104
A polymorphic fibro-osseous lesion of the bone is a benign fibro-osseous lesion of the bone with a marked predilection for the proximal femur and characterized by a complex mixture of histological elements. We present one such case of a 35-year-old female with spontaneous onset of pain in the left hip for 3 months and trauma sustained a year ago. An examination revealed tenderness with painful movements over the anterior aspect of the left hip joint and trochanter. A clinico-radiological differential diagnosis of simple bone cyst or fibrous dysplasia was entertained. A microscopic examination of the lesion with clinico-radiologic correlation led to the diagnosis of a polymorphic fibro-osseous lesion. This is a genuine clinico-pathologic entity that is usually asymptomatic with a rare history of trauma or hip pain. It has a distinctive histopathological picture with a better prognosis than its mimics.
|How to cite this article:|
Rao AC, Rao CG. Polymorphic fibro-osseous lesion of the bone: A case report with review of literature.Indian J Pathol Microbiol 2008;51:538-540
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Rao AC, Rao CG. Polymorphic fibro-osseous lesion of the bone: A case report with review of literature. Indian J Pathol Microbiol [serial online] 2008 [cited 2021 Oct 16 ];51:538-540
Available from: https://www.ijpmonline.org/text.asp?2008/51/4/538/43754
A polymorphic fibro-osseous lesion of the bone, alluded to earlier as a liposclerosing myxofibrous tumor, is an entity with site-specific occurrence characterised by a peculiar juxtaposition of histological patterns individually typical of several distinct entities.
This article seeks to discuss one such case and review literature about the peculiarities of this distinct lesion.
A 35-year-old female presented with a history of spontaneous onset of pain in the left hip for 3 months. A history of trauma sustained a year back was elicited. On examination, tenderness was noted over the anterior aspect of the left hip joint and trochanter with painful terminal range of movements. An X-ray [Figure 1] revealed a large expansile lytic lesion with ground glass appearance and a narrow zone of transition involving the proximal metadiaphyseal region of the left femur with endosteal scalloping. No evidence of a cortical break, soft tissue extension, or calcification was noted. The erythrocyte sedimentation rate (ESR) was 22 mm. A clinico-radiological differential diagnosis of simple bone cyst/fibrous dysplasia was entertained and a specimen was sent for histopathological examination.
The specimen was sent as multiple glistening membranous bony bits of tissue with specks of yellow and areas of hemorrhage.
Microscopically, a lesion composed of sheets of loosely cellular fibrous tissue with plump fibroblasts with vesicular fusiform nucleus, thin C-shaped bony spicules [Figure 1], without osteoblastic rimming was seen. Focal areas also showed irregularly interspersed thick bone amongst the cellular spindle cell area [Figure 2] also seen were. Stromal myxoid change, [Figure 3], multivacuolated cells; hyalinization, aggregates of foamy histiocytes [Figure 2] and [Figure 3] with few lymphocytes and thin walled blood vessels interspersed. [Figure 3].
Polymorphic fibro-osseous lesion of the bone is a benign condition and is thought to be acquired as an aberration of growth and development in childhood.  Also known as polymorphic fibrous dysplasia, atypical fibrous dysplasia, and polymorphic fibrocystic disease of the bone by various pathologists worldwide, it is a rarity in literature. This is surmised from the fact that some regard it as a variant of fibrous dysplasia; others assume it to be secondary to degenerative changes in other benign lesions like simple bone cyst, lipoma, fibromyxoma, fibrous dysplasia, and bone infarcts. ,, Occurring in a wide age range, it is a clinical incidental discovery on X-rays obtained for unrelated medical causes. These lesions lack distortion of bony outline indicating stability in size over many years. However, few lesions do enlarge with secondary fractures or infarctions making them painfully symptomatic. ,
Distinct to the femur, the area most often involved is the intertrochanteric zone, with a few cases involving the subtrochanteric area. Ragsdale, in his extensive study on these lesions, does mention 10% of such tumors to occur in other sites namely the distal femur, tibia, humerus, and calvarium. ,
Radiologically,  these lesions are large with accurately defined margins. A proximal pointed border resembling the bow of the ship, irregular densities, and cystic change characterize it. If the distal margin exceeds the lesser trochanter, it slopes medially across the marrow space conclusively differentiating it from a bone infarct. In fibrous dysplasia, the outlines are less well-defined. Enchondroma, chondromyxoid fibroma, desmoplastic fibromas, bone cysts, and intraosseous lipomas do not demonstrate the reinforced outlines, irregular densities, or focal cystic changes that characterize this lesion. 
Pathologically, these lesions are characterized by a conglomerate of patterns reminiscent of nonossifying fibroma, fibrous dysplasia, Paget's disease, lipoma, bone infarct, etc. The various tissue types coexist side by side in various sections of the lesion. Lipomatous areas show mature fat cells, or less often, multivesicular fat filled cells. An overlap with fibrous dysplasia is seen in metaplastic curvilinear or circular bone without active osteoblastic rimming in a bed of spindle cell stroma. Besides this, Pseudopaget and woven bone can also be seen, especially in the fibroxanthoma areas, which also show the multivesicular fat-filled cells. , Myxoid foci show stellate cells in a loose collagenous background. Fibrous areas may also show a storiform pattern, which, in a poorly sampled specimen, may lead to a misdiagnosis of fibrous histiocytoma of the bone. 
In younger individuals, areas of plump spindle cells may predominate. Reports of cystic change in the lesion with mineralization of the walls have been documented. In older patients, sarcomatous changes may occur, though rarely. This is thought to be secondary to either ischemic desmoplasia or from the fibroxanthomatous areas turning malignant. Cases reported also include malignant high-grade spindle cell sarcomas. ,
Differentiation from an infarct either per se or in fibrous dysplasia, requires a careful study of the radiological and histopathological findings. Poor sampling may cause a misdiagnosis of fibrous histiocytoma, lipoma,  fibroxanthoma, aneurysmal bone cyst, or even Paget's disease. In all these cases, characteristic site and radiology help in differentiation. Often regarded by some as a variant of fibrous dysplasia, it has of late come into its own. ,
A polymorphous fibro-osseous lesion of the bone is a distinct lesion of the proximal femur with an intertrochanteric preference, characterestic radiological picture, and an admixture of patterns of varied other bone lesions. Awareness of the lesion and its features may prevent a misdiagnosis, especially in poorly sampled cases.
We acknowledge the contribution of Dr. Anuj Khurana in acquisition of the data essential for this article.
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