The molecular events that precede the development of osteosarcoma, the most common primary malignancy of bone, are unclear, and concurrent molecular and genetic alterations associated with its pathogenesis have yet to be identified. Recent studies suggest that activation of ␤-catenin signaling may play an important role in human tumorigenesis. To investigate the potential role of ␤-catenin deregulation in human osteosarcoma, we analyzed a panel of 47 osteosarcoma samples for ␤-catenin accumulation using immunohistochemistry. Potential activating mutations were investigated by sequencing exon 3 of the ␤-catenin gene in genomic DNA isolated from tumor samples. Our findings revealed cytoplasmic and/or nuclear accumulation of ␤-catenin in 33 of 47 samples (70.2%); however, mutation analysis failed to detect any genetic alterations within exon 3, suggesting that other regulatory mechanisms may play an important role in activating ␤-catenin signaling in osteosarcoma. In our survival analysis, ␤-catenin deregulation conferred a hazard ratio of 1.05, indicating that ␤-catenin accumulation does not appear to be of prognostic value for osteosarcoma patients. When analyzed against other clinicopathologic parameters, ␤-catenin accumulation correlated only with younger age at presentation (26.4 vs. 39.8 years). Nevertheless, our results demonstrate that the deregulation of ␤-catenin signaling is a common occurrence in osteosarcoma that is implicated in the pathogenesis of osteosarcoma. © 2002 Wiley-Liss, Inc. Key words: Wnt signal; ␤-catenin; osteosarcoma; tumorigenesis; bone tumorOsteosarcoma is the most common primary malignant tumor of bone, encompassing a class of osteoid-producing neoplasms that range in clinical behavior and responsiveness to therapeutic regimens. 1 Best known of these lesions, the classic high-grade osteosarcoma, primarily afflicts individuals in the second decade of life and is distinguished by its locally aggressive character and early metastatic potential. Despite advances in chemotherapy, 5-year survival has remained around 60%. 2 The molecular events that precede the development of osteosarcoma are poorly understood. Given its relatively early age at presentation and predilection for early metastasis, osteosarcoma is likely the result of underlying early somatic and/or germline mutations. Alterations in tumor-suppressor genes such as retinoblastoma (Rb1) and p53 have been identified in osteosarcoma and hypothesized to predispose individuals to this malignancy at an especially early age. [3][4][5][6] Although several putative chromosomal regions have been suggested to harbor potential tumor-suppressor genes, the molecular nature and identity of these genes have not been elucidated.␤-Catenin is a cellular protein with multiple functions. As an important component of the adherens junction complex, it helps to anchor E-cadherin to the intracellular actin cytoskeleton through interactions with ␣-catenin. 7,8 As an important Wnt signal transducer, ␤-catenin plays an important role in many developmental...

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BACKGROUND. Telangiectatic osteosarcoma (TOS) isRESULTS. Among 323 patients with OS, 22 patients (6.8%) had TOS. Two additional patients who were treated in Chile on a recent OS trial were included. The median age at diagnosis of the 24 patients was 15.7 years. Four patients (17%) had metastatic disease, and 9 of 21 patients (43%) had pathologic fractures. Only 5 patients (who were treated after 1994) underwent limb-salvage surgery.Estimates of 5-year event-free survival (58.3% AE 11.9%) and overall survival (66.8% AE 11.6%) were similar to those for patients with other OS subtypes (P ! .85). The absence of local disease progression and chemotherapy with !3 agents that were active against OS were correlated with improved outcome (P .005).The presence of a pathologic fracture was not associated with surgery type or patient outcome.CONCLUSIONS. TOS was associated with a high rate of pathologic fracture. With multimodality therapy, the outcome of patients with TOS was similar to that of patients with other high-grade OS subtypes. The absence of local disease progression and chemotherapy with !3 active agents were associated with a favorable outcome.