No abstract

The BCOR-CCNB3 fusion gene, resulting from a chromosome X paracentric inversion, was recently described in translocation-negative ‘Ewing-like’ sarcomas arising in bone and soft tissue. Genetic subclassification of undifferentiated unclassified sarcomas may potentially offer markers for reproducible diagnosis and substrates for therapy. Using whole transcriptome paired end RNA sequencing (RNA-seq) we unexpectedly identified BCOR-CCNB3 fusion transcripts in an undifferentiated spindle cell sarcoma. RNA-seq results were confirmed through direct RT-PCR of tumor RNA and cloning of the genomic breakpoints from tumor DNA. Five additional undifferentiated sarcomas with BCOR-CCNB3 fusions were identified in a series of 42 pediatric and adult unclassified sarcomas. Genomic breakpoint analysis demonstrated unique breakpoint locations in each case at the DNA level even though the resulting fusion mRNA was identical in all cases. All patients with BCOR-CCNB3 sarcoma were males diagnosed in mid-childhood (7-13 years of age). Tumors were equally distributed between axial and extra-axial locations. Five of the six tumors were soft tissue lesions with either predominant spindle cell morphology or spindle cell areas interspersed with ovoid to round cells. CCNB3 immunohistochemistry showed strong nuclear positivity in 5 tumors prior to oncologic therapy, but was patchy to negative in post-treatment tumor samples. An RT-PCR assay developed to detect the fusion transcript in archival formalin-fixed tissue was positive in all 6 cases, with high sensitivity and specificity in both pre- and post-treated samples. This study adds to recent reports on the clinicopathologic spectrum of BCOR-CCNB3 fusion-positive sarcomas, a newly-emerging entity within the undifferentiated unclassified sarcoma category, and describes a simple RT-PCR assay that in conjunction with CCNB3 immunohistochemistry can be useful in diagnosing these tumors.

Myxofibrosarcoma is a unique subtype of soft tissue sarcoma with a locally infiltrative behavior. High-quality MRI imaging is critical for preoperative planning. Wide surgical resection with a 2 cm soft tissue margin is the mainstay of treatment and can require complex vascular and plastic surgery reconstruction. Local recurrence is common, and a subset of patients with higher-grade lesions will develop distant metastases. Radiation may be beneficial in reducing local recurrence.

The molecular determinates involved in the progression of myxoid liposarcoma to increased cellularity/round cell change are poorly understood. We studied the PI3K/Akt pathway in myxoid and round cell liposarcomas using a tissue microarray composed of 165 tumors from 111 patients, and mutational analysis of PIK3CA in 44 cases. Activating PIK3CA mutations were found in 6/44 cases, 14%; mutations were more frequent in round cell vs. myxoid tumors (5/15, 33% vs. 1/29, 3%; p=0.013). Complete loss of PTEN, an alternative mechanism for PI3K/Akt activation, was found in 13/111 (12%) cases and was mutually exclusive with PIK3CA mutation. Strong IGF1R expression was demonstrated in 14/39 (36%) of round cell and 11/58 (19%) of myxoid tumors (p=0.062). Activation of the PI3K pathway was confirmed using immunohistochemical analysis for downstream targets phospho-S6 ribosomal protein and phospho-4EBP1. Phospho-4EBP1 was increased in round cell tumors compared to myxoid tumors (24/30, 80% vs. 25/44, 57%; p=0.038) or tumors with treatment effect (10/24, 42%; p=0.02). Phospho-S6 was highly expressed in both myxoid and round cell tumors (29/47, 62% and 14/30, 47%, respectively; p=0.2). In tumors with PIK3CA mutation, any IGF1R expression, or loss of PTEN expression, phospho-4EBP1 was more frequently elevated compared to tumors without a known activating event in the PI3K pathway (55/72; 76% vs. 3/8, 38%; p=0.033). These findings suggest that activation of the PI3K/Akt pathway via activating mutation of PIK3CA, loss of PTEN, or IGF1R expression play a role in round cell transformation. The PI3K/Akt pathway may therefore provide a therapeutic target in round cell liposarcoma.

BackgroundPatients with advanced solitary fibrous tumors (SFTs) have a poor prognosis; treatment options for recurrent disease are particularly limited. Several novel targeted agents have recently shown promise against advanced SFTs, but the relative efficacy of new agents is difficult to assess because data on the efficacy of conventional chemotherapy for SFTs are limited. We thus sought to estimate the efficacy of conventional chemotherapy for SFTs by reviewing data on tumor response to therapy and progression-free survival from SFT patients who received this therapy.MethodsWe retrospectively analyzed the clinical outcomes of 21 patients with grossly measurable, advanced SFTs (unresectable metastatic disease or potentially resectable primary tumors) who received conventional chemotherapy and follow-up at The University of Texas MD Anderson Cancer Center between January 1994 and June 2007. Best tumor response to therapy was assessed using the Response Evaluation Criteria In Solid Tumors 1.1. The Kaplan-Meier method was used to estimate median progression-free survival (PFS) duration.ResultsOf 21 patients, 4 received more than 1 regimen of chemotherapy, for a total of 25 treatments. Doxorubicin-based chemotherapy was given in 15 cases (60%), gemcitabine-based therapy in 5 cases (20%), and paclitaxel in 5 cases (20%). First-line chemotherapy was delivered in 18 cases (72%). No patients had a complete or partial response, 16 (89%) had stable disease, and 2 (11%) had disease progression. Five patients (28%) maintained stable disease for at least 6 months after first-line treatment. The median PFS duration was 4.6 months. The median overall survival from diagnosis was 10.3 years.ConclusionConventional chemotherapy is effective in controlling or stabilizing locally advanced and metastatic SFTs. Our findings can serve as a reference for tumor response and clinical outcomes in the assessment of novel treatments for SFTs.