title: [Low-grade central osteosarcoma: a clinicopathologic analysis of nine cases].
abstract: OBJECTIVE
  to study the clinicopathologic features and differential diagnosis of low-grade central osteosarcoma (LGCOS).
  
  
  METHODS
  nine cases of LGCOS were retrieved from the archival consultation files. The clinical, radiologic and pathologic features were analyzed, with literature review.
  
  
  RESULTS
  the mean age of the patients was 31 years. The male-to-female ratio was 3:6. All of the patients presented with painful mass and/or swelling. The sites of involvement included thigh (n = 4), tibia (n = 1), fibula (n = 1), cervical vertebra (n = 1), lumbar vertebra (n = 1) and maxilla (n = 1). Radiologic examination showed mixed lytic/blastic lesions with soft tissue shadow in 5 cases and associated periosteal reaction in 3 cases. The tumors were treated by surgical excision, with no adjuvant therapy given. The duration of follow up ranged from 2 to 43 months. Four cases had recurrence which occurred at 8 to 25 months after the operation. Gross examination showed that the tumors were fragmented on submission in 5 cases and en bloc in 4 cases. They had solid and firm cut surface, with various degree of grittiness. Histologically, LGCOS was characterized by the presence of hypocellular fibroblastic stroma associated with focal osteoid production. The spindly tumor cells showed mild degree of nuclear pleomorphism, with occasional mitotic figures demonstrated in all of the 9 cases. The newly formed neoplastic woven bone did not have any osteoblastic rimming. The bony trabeculae were slender and seam-like. Parallel arrays of woven bone were seen in 6 cases. Some of the bony trabeculae appeared irregularly branched and curved. The tumor cells permeated adjoining pre-existing bony trabeculae and bone marrow in all cases. Three cases also showed soft tissue involvement.
  
  
  CONCLUSIONS
  LGCOS often posses important diagnostic pitfalls due to the relatively bland-looking tumor cell morphology and associated large woven or longitudinal seams of lamellar-like bone. Thorough understanding of the histologic features, when coupled with clinical and radiologic findings, are essential in arriving at a correct diagnosis.
authors.affiliation: Department of Pathology, Institute of Cancer Research, Cancer Hospital, Fudan University and Department of Oncology, Shanghai Medical College, Shanghai 200032, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yu
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Chao-Fu
authors.initials: CF
authors.lastname: Wang
authors.forename: Xiong-Zeng
authors.initials: XZ
authors.lastname: Zhu
mesh_terms: D000293:Adolescent; D000328:Adult; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D005357:Fibrous Dysplasia of Bone / Q000473:pathology; D005360:Fibula / Q000000981:diagnostic imaging; D018219:Histiocytoma, Benign Fibrous / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D012516:Osteosarcoma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D011859:Radiography; D011877:Radionuclide Imaging; D012086:Reoperation; D013848:Thigh / Q000000981:diagnostic imaging / Q000473:pathology; D055815:Young Adult