Fibrosarcoma

17 Fibrosarcoma Antonieta Solar Abstract Fibrosarcoma is a malignant bone tumor that grows rapidly; it looks like an osteosarcoma with no forming osteoid tissue. Keywords Fibrosacoma
Malign bone sarcoma Fibrosarcoma is a malignant tumor deriving from fibroblasts. It is a rare bone tumor more frequently found in the soft tissues [1–3]. Osseous fibrosarcoma is presented across all age ranges, being more frequent in adults within the fourth to sixth decades. The distal femur and proximal tibia are the most frequent locations.The ratio of male:female is not revelant. As with other malign bone tumors its clinical presentation begins with dull pain and local swelling which can be palpated like a mass. Symptoms appear in weeks or a few months. Imaging Fibrosarcoma has a metaphyseal or diaphyseal location like a osteolytic, poorly marginated lesion (distal femur more frequent), destroying the cortical without periostic reaction or sclerosis, and can show invasion of soft tissues. There is a risk of pathological fracture. Macroscopic Pathology About two-thirds of fibrosarcomas measure 9 cm or less and the rest 10 cm or more at their largest dimension. The gross appearance of these tumors depends on their grade; low A. Solar (&) Pontificia Universidad Católica de Chile, Santiago, Chile e-mail: asolar@med.puc.cl © Springer-Verlag London Ltd., part of Springer Nature 2021 J. Paulos and D. G. Poitout (eds.), Bone Tumors, https://doi.org/10.1007/978-1-4471-7501-8_17 grade tumors are usually grayish to white, firm and rubbery, with a whorled cut surface or they can be soft and friable, with a evidently permeative pattern in high grade tumors, which may show areas of necrosis, hemorrhage, cystic degeneration or rarely, myxoid areas. Most tumors destroy the cortex. Microscopic Pathology Fibrosarcomas consists of interlacing fascicles of spindle cells arranged in a “herringbone” pattern in the majority of cases [4]. The nuclei are elongated and thin, with a fine or granular chromatin often with nucleoli and tapered ends. The cytoplasm is usually indistinguishable. The amount of collagen varies, ranging from slight to massive in well-differentiated fibrosarcomas. The tumor has a permeative growth pattern, leaving entrapped pre existent bone trabeculae in the lesion. Rarely, the tumor may be markedly myxoid or consist of small cells suggestive of Ewing’s sarcoma. The grade of fibrosarcomas correlates well with the prognosis, hence the importance of grading these tumors. The four-grade Broders’ system has been widely use, although some authors prefer to use a two- or three-grade system, both methods depending upon the production. The cells are fusiform with slight pleiomorphism, if any. The nuclei are ovoid or slender, some can be plump, with fine chromatin and little hyperchromasia. Nucleoli are inconspicuous and small. The mitotic count is low. High grade or poorly differentiated (Broders’ III and IV) fibrosarcomas are exceedingly cellular and have scarce or no collagen production. The cells are spindle shaped and plump with moderated pleiomorphism; some cells are multinucleated; the nuclei are very dense, have fine and coarse irregular clumps of chromatin with hyperchromasia. Nucleoli can be small or large, but inconsistent; the mitotic count is overtly high. Foci of necrosis, hemorrhage or myxoid stroma are common. 127 128 Special Techniques: Fibrosarcoma cells are strongly positive for vimentin and focally positive with smooth muscle actin. Microscopic Differential Diagnosis Well-differentiated fibrosarcoma differential diagnosis includes fibrous dysplasia and desmoplastic fibroma. The cells of fibrous dysplasia are usually plump, while fibrosarcoma cells are slender. No mineralized matrix should be found in fibrosarcoma, while the finding of “alphabet” appearing metaplastic bone formation confirms the diagnosis of fibrous dysplasia. Trying to distinguish between well-differentiated fibrosarcoma and desmoplastic fibroma is very complicated. Fibrosarcoma should have at least in some areas nuclear pleiomorphism, slight mitotic activity and a “herringbone” pattern. Poorly differentiated fibrosarcoma differential diagnosis includes fibroblastic osteosarcoma, malignant fibrous histiocytoma, spindle cell or sarcomatoid carcinoma and spindle cell melanoma. The identification of the osteoid matrix supports the diagnosis of osteosarcoma. A storiform pattern, epitheliod cells and evident cellular pleiomorphism favor malignant fibrous histiocitoma, obvious pleiomorphism is not a distinguishing quality of the fibrosarcoma cells. Spindled carcinoma cells or melanoma cells are usually distinguished by a good clinical history and immunohistochemical techniques for epithelial markers or melanocitic markers, respectively. A. Solar Treatment Pre-operative chemotherapy similar to osteosarcoma can be indicated plus wide resection if posible with a wide surgical margin or amputation [5, 6]. 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