Shih-Chen Yu

Skp2 is an independent prognosticator of gallbladder carcinoma among p27(Kip1)-interacting cell cycle regulators: an immunohistochemical study of 62 cases by tissue microarray.

Despite improvement in surgical techniques, prognosis of gallbladder carcinoma remains poor. It is desirable to identify prognostic biomarkers to aid in the development of targeted therapeutic strategies. Two SCFSkp2 ubiquitin ligase-related proteins, Skp2 and cyclin-dependent kinase subunit 1 (Cks1), are involved in post-transcriptional degradation of p27Kip1 tumor suppressor, which inhibits both cdk2/cyclin E and cdk2/cyclin A complexes and thus prevents transition to the S phase. However, the prognostic utility of p27Kip1-interacting cell cycle regulators has not been systematically assessed in gallbladder carcinoma. Immunohistochemistry was performed for p27Kip1, Skp2, Cks1, cyclin E, cyclin A, and Ki-67 in tissue microarrays of 62 gallbladder carcinomas with follow-up. The data were correlated with clinicopathological features and overall survival (OS). The cumulative OS rate for all 62 cases was 42.9% at 3 years. Aberrant labeling indices (LIs) of p27Kip1 (<20%), cyclin E (≥5%), cyclin A (≥5%), Cks1 (≥40%), and Skp2 (≥10%) were identified in 29, 58, 66, 21, and 57% of gallbladder carcinomas, respectively. By log-rank tests, downregulation of p27Kip1 (P=0.0319) and high LIs of Skp2 (P=0.0006), Cks1 (P=0.0460), cyclin E (P=0.0070), and Ki-67 (P=0.0037) were predictive of inferior OS. Furthermore, the combined expression status of Skp2 and Ki-67 robustly defined three prognostically different groups (P=0.0001). In multivariate comparison, Skp2 overexpression represented the strongest independent adverse prognosticator (P=0.004, risk ratio (RR): 5.538), followed by Ki-67 LI ≥50% (P=0.016, RR: 3.254) and American Joint Committee on Cancer stages II–IV (P=0.013, RR: 3.163). In conclusion, aberrations of p27Kip1-interacting cell cycle regulators are common in gallbladder carcinomas. Skp2 overexpression is highly representative of biological aggressiveness and independently associated with poor OS, suggesting that it is a promising novel target for therapeutic intervention in aggressive cases. The combined assessment of Skp2 and Ki-67 LIs effectively risk-stratifies gallbladder carcinomas with different prognosis, which is worth being prospectively validated in future study.

NAB2–STAT6 fusion types account for clinicopathological variations in solitary fibrous tumors

Solitary fibrous tumor (SFT) is characterized by the inv12(q13q13)-derived NAB2–STAT6 fusion, which exhibits variable breakpoints and drives STAT6 nuclear expression. The implications of NAB2–STAT6 fusion variants in pathological features and clinical behavior remain to be characterized in a large cohort of SFTs. We investigated the clinicopathological correlates of this genetic hallmark and analyzed STAT6 immunoexpression in 28 intrathoracic, 37 extrathoracic, and 23 meningeal SFTs. These 88 tumors were designated as histologically nonmalignant in 75 cases and malignant in 13, including 1 dedifferentiated SFT. Eighty cases had formalin-fixed and/or fresh samples to extract assessable RNAs for RT-PCR assay, which revealed NAB2–STAT6 fusion variants comprising 12 types of junction breakpoints in 73 fusion-positive cases, with 65 (89%) falling into 3 major types. The predominant NAB2ex4–STAT6ex2 (n=33) showed constant breakpoints at the ends of involved exons, whereas the NAB2ex6–STAT6ex16 (n=16) and NAB2ex6–STAT6ex17 (n=16) might exhibit variable breakpoints and incorporate NAB2 or STAT6 intronic sequence. Including 73 fusion-positive and 7 CD34-negative SFTs, STAT6 distinctively labeled 87 (99%) SFTs in nuclei, exhibited diffuse reactivity in 73, but did not decorate 98 mimics tested. In seven fusion-negative cases, 6 were STAT6-positive, suggesting rare fusion variants not covered by RT-PCR assay. Regardless of histological subtypes, intrathoracic SFTs affected older patients (P=0.035) and tended to be larger in size (P=0.073). Compared with other variants, NAB2ex4–STAT6ex2/4 fusions were significantly predominant in the SFTs characterised by intrathoracic location (P<0.001), older age (P=0.005), decreased mitoses (P=0.0028), and multifocal or diffuse STAT6 staining (P=0.013), but not found to correlate with disease-free survival. Conclusively, STAT6 nuclear expression was distinctive in the vast majority of SFTs, including all fusion-positive tumors, and exploitable as a robust diagnostics of CD34-negative cases. Despite the associations of NAB2–STAT6 fusion variants with several clincopathological factors, their prognostic relevance should be further validated in large-scale prospective studies of SFTs.

Heat Shock Protein 90 Overexpression Independently Predicts Inferior Disease-Free Survival with Differential Expression of the α and β Isoforms in Gastrointestinal Stromal Tumors

Purpose: Most gastrointestinal stromal tumors harbor a mutated KIT or PDGFRA receptor tyrosine kinase (RTK). Heat shock protein 90 (Hsp90) is a chaperone mediating the folding and stabilization of many oncoproteins, including KIT. An Hsp90 inhibitor, 17-AAG, can attenuate KIT activation and proliferation of gastrointestinal stromal tumor cell lines. We further evaluated Hsp90 immunoexpression and the difference between α and β isoforms in gastrointestinal stromal tumor specimens. Experimental Design: Hsp90 immunostain was assessable in 306 cases on tissue microarrays of primary gastrointestinal stromal tumors and correlated with various variables and disease-free survival (DFS). RTK mutation variants, confirmed in 142 cases by sequencing with or without precedent denaturing high pressure liquid chromatography screening, were dichotomized into two prognostically different groups. Differential expression of transcript and protein isoforms was measured by real-time reverse transcription-PCR and Western blotting in 16 and 6 cases, respectively. Results: Hsp90 overexpression (55%) significantly correlated with larger size, nongastric location, higher mitotic count and NIH risk level, Ki-67 overexpression (all P ≤ 0.001), and unfavorable RTK genotypes (P = 0.020). It strongly portended inferior DFS univariately (P < 0.0001) and remained independent in multivariate analysis (P = 0.031; risk ratio, 2.44), along with high-risk category, Ki-67 overexpression, and old age. For both mRNA and protein, Hsp90β was more abundant than Hsp90α, whereas the latter was significantly higher in high-risk cases. Conclusions: Hsp90 overexpression represents a poor prognosticator that correlates with several adverse parameters, highlighting its role in disease progression and alternative therapy for high-risk, imatinib-resistant gastrointestinal stromal tumors. Hsp90α seems more relevant to the intrinsic aggressiveness of gastrointestinal stromal tumors, albeit less abundant than Hsp90β.

Malignant diffuse-type tenosynovial giant cell tumors: a series of 7 cases comparing with 24 benign lesions with review of the literature.

Background Malignant diffuse-type tenosynovial giant cell tumor (D-TSGCT), an unusual sarcoma with concurrent or previous benign D-TSGCTs, poses challenges to diagnosis and prognostication. Methods We described the radiologic, clinicopathologic, and immunophenotypical findings of 5 primary and 2 metachronous malignant D-TSGCTs and reviewed published cases to better delineate their morphologic spectrum and behavior. Twenty-four benign D-TSGCTs were also statically compared to analyze the diagnostic values of various variables. Results The 7 malignant cases affected 4 females and 3 males aged 45 to 78 (mean, 60.9) years, which included 1 intra-articular and 6 extra-articular lesions. These tumors were 5 to 17 cm (mean, 9.4) and located within or near the large joints of extremities. Magnetic resonance imaging revealed expansile or infiltrative masses with frequent lobulation and heterogeneous signals. Histologically, areas of benign D-TSGCTs blended abruptly or gradually with frank sarcomas composed of pleomorphic, spindle, or enlarged oval cells, forming malignant fibrous histiocytomalike (n=4), fibrosarcomatous (n=1), myxosarcomatous (n=1), or giant cell tumorlike (n=1) patterns. One patient experienced recurrences twice, and another 3 developed metastases to the lymph nodes (n=2), lung (n=1), or vertebrae (n=1), with 1 dying from disseminated diseases. An older age (P=0.003), a larger size (P=0.036), tumor necrosis (P<0.001), atypical mitoses (P<0.001), and Ki-67 overexpression (P<0.001) appeared preferentially in malignant lesions, but these parameters had overlap between few benign and malignant tumors. Conclusions Malignant D-TSGCTs are a distinct sarcoma with considerable morphologic variability, metastatic propensity, and lethality. Altered architecture with anaplastic cells represents an important distinguishing feature, while abnormalities of other parameters should not be directly equated with malignancy.

Homozygous Deletion of MTAP Gene as a Poor Prognosticator in Gastrointestinal Stromal Tumors

Purpose: Chromosome 9 is frequently deleted in high-risk gastrointestinal stromal tumors (GISTs), whereas its specific tumor suppressor genes (TSGs) are less understood. We did an integrative study of MTAP gene at 9p21 to analyze its implication in GISTs. Experimental Design: To search TSGs on chromosome 9, we used ultrahigh-resolution array comparative genomic hybridization to profile DNA copy number alterations of 22 GISTs, with special attention to MTAP gene. MTAP immunoexpression was assessable for 306 independent GISTs on tissue microarrays, with 146 cases analyzed for MTAP homozygous deletion, 181 for mutations of KIT and PDGFRA receptor tyrosine kinase genes, and 7 for MTAP hypermethylation. Results: Array comparative genomic hybridization identified 11 candidate TSGs on 9p and six on 9q. MTAP and/or CDKN2A/CDKN2B at 9p21.3 were deleted in one intermediate-risk (11) and seven high-risk (70) GISTs with two cases homozygously codeleted at both loci. MTAP homozygous deletion, present in 25 of 146 cases, was highly associated with larger size and higher mitotic rate, Ki-67 index, and risk level (all P < 0.01) but not with receptor tyrosine kinase genotypes. Whereas MTAP homozygous deletion correlated with MTAP protein loss (P < 0.001), 7 of 30 GISTs without MTAP expression did not show homozygous deletion, including three MTAP-hypermethylated cases. MTAP homozygous deletion was univariately predictive of decreased disease-free survival (P < 0.0001) and remained multivariately independent (P = 0.0369, hazard ratio = 2.166), together with high-risk category (P < 0.0001), Ki-67 index >5 (P = 0.0106), and nongastric location (P = 0.0416). Conclusions:MTAP homozygous deletion, the predominant mechanism to deplete protein expression, is present in 17 of GISTs. It correlates with important prognosticators and independently predicts worse outcomes, highlighting the role in disease progression. (Clin Cancer Res 2009;15(22):696372)

Ezrin overexpression in gastrointestinal stromal tumors: an independent adverse prognosticator associated with the non-gastric location

Ezrin, a member of the ezrin–radixin–moesin family, acts as a link between the cell membrane and actin cytoskeleton to integrate cell adhesion-mediated signaling. It implicates tumor progression, metastatic dissemination, and adverse outcomes in several cancer types, including pediatric and adult sarcomas. Although ezrin upregulation was shown by cDNA expression profiling, no study has systematically evaluated the significance of ezrin expression in a large cohort of gastrointestinal stromal tumors (GISTs). Ezrin immunostaining was carried out on tissue microarrays of primary GISTs and assessable in 347 cases, 188 of which were successfully evaluated for mutation variants of KIT and PDGFRA receptor tyrosine kinase (RTK) genes by sequencing with or without screening by denatured high-performance liquid chromatography. These GISTs with known RTK genotypes were dichotomized into two prognostically different groups. The endogenous expression and phosphorylation of ezrin in GIST cell lines were analyzed by western blotting. By immunohistochemistry, ezrin overexpression was present in 66% of GISTs and significantly associated with the non-gastric location (P=0.002) and decreased disease-free survival (P=0.032, univariately). However, it was not related to the National Institute of Health (NIH) risk category, Ki-67 labeling index, RTK genotypes, and other variables. In multivariate analyses, ezrin overexpression remained independently predictive of adverse outcome (P=0.008, risk ratio=2.363), together with Ki-67 labeling index >5% (P<0.001, risk ratio=3.581), high-risk category (P<0.001, risk ratio=2.156), and the non-gastric location (P=0.029, risk ratio=1.899). Despite the variation in the ezrin expression level, phosphorylated ezrin at threonine567 was only detectable in GIST882 and GIST48 cells, but not in colonic smooth muscle cells. In conclusion, ezrin is frequently overexpressed in GISTs, especially those arising from the non-gastric sites. Given that its impact is independent of the NIH risk category, cell proliferation, and tumor location, ezrin immunoreactivity represents a valuable prognostic adjunct of GISTs, suggesting a causative role in conferring an aggressive phenotype.

Angiomatoid fibrous histiocytoma: clinicopathological and molecular characterisation with emphasis on variant histomorphology

Aims Angiomatoid fibrous histiocytoma (AFH) is histologically typified by nodules of histiocytoid spindle cells with pseudoangiomatoid spaces, fibrous pseudocapsules and lymphocytic cuffs. The principal goal was to expand the spectrum of AFHs through clinicopathological and molecular characterisation. Methods Thirteen AFHs, including 11 with confirmed hallmark translocation, were reappraised for classic features, reactive osteoclasts, mitoses and stromal, architectural and cytomorphological variations, with CD99, desmin and EMA stained in available cases. Results Seven male and six female patients ranged in age from 4 to 63 years (median, 13), including 4 older than 20 years. Tumours were located on the extremities (n=6), trunk (n=4) and scalp (n=3). Although fibrous pseudocapsules were observed in all cases, four showed solid histology without pseudoangiomatoid spaces and another one lacked peripheral lymphoid infiltrates. Nuclear pleomorphism was striking in two cases, moderate in seven and absent in four, with osteoclasts seen in two cases. In three AFHs with sclerotic matrix, one exhibited perivascular hyalinisation and nuclear palisading, reminiscent of a schwannoma. In three varyingly myxoid tumours, one closely resembled a myoepithelioma with prominent reticular arrangement of spindle cells in an abundant myxoid stroma. Besides EWSR1 gene rearrangement detected in four cases by fluorescence in situ hybridisation (FISH), EWSR1-CREB1 fusion was confirmed in nine cases, including a schwannoma-like AFH, and EWSR1-ATF1 fusion detected in a myoepithelioma-like AFH. Immunohistochemically, 56% of AFHs were positive for EMA, 78% for desmin and 100% for CD99. Conclusions Molecular testing is diagnostic of variant AFHs displaying diverse histomorphological alterations in the architectural patterns, cytomorphology and extracellular matrix.

The clinicopathological significance of NAB2‐STAT6 gene fusions in 52 cases of intrathoracic solitary fibrous tumors

NAB2‐STAT6 gene fusion drives STAT6 nuclear expression and is the pathognomonic hallmark of solitary fibrous tumors (SFTs). However, no study has systematically analyzed the clinicopathological features, STAT6 immunoexpression status, or the fusion variants of NAB2‐STAT6 in intrathoracic SFTs. Fifty‐two intrathoracic SFTs were retrieved to appraise histopathology, assess STAT6 immunoexpression, and determine NAB2‐STAT6 fusion variants by RT‐PCR. Location‐relevant histologic mimics served as controls. Thirty‐one pleura‐based, 12 mediastinal/pericardial, and nine intrapulmonary lesions were histologically categorized into eight malignant, eight atypical, and 36 conventional or cellular SFTs, including two fat‐forming and two giant cell angiofibroma‐like SFTs. STAT6 distinctively decorated the tumoral nuclei in 51 (98%) SFTs. However, no nuclear staining was observed in the histological mimics. NAB2‐STAT6 fusion was detected in 34 SFTs. Twenty‐nine (85.3%) exhibited the major NAB2ex4‐STAT6ex2/3 variant and 5 (14.7%) the minor NAB2ex6‐STAT6ex16/17. NAB2ex4‐STAT6ex2 was significantly associated with older age (P = 0.01) and pleuropulmonary tumors (P = 0.025). After a median follow‐up of 33.9 (range, 0.3–174.6) months, adverse outcomes occurred in one atypical and five malignant SFTs, including two local relapses, one intrapulmonary metastasis, and three extrathoracic metastases. Inferior disease‐free survival was univariately associated with atypical/malignant histology (P = 0.001) and a mitosis >4/10 HPFs (P = 0.0012) but was unrelated to fusion variants. In conclusion, the majority of intrathoracic SFTs exhibited STAT6 nuclear staining, and NAB2ex4‐STAT6ex2/3 was the predominant fusion type. However, clinical aggressiveness is associated with atypical/malignant histology primarily contributed by increased mitosis but was unrelated to the NAB2‐STAT6 fusion variants.

Immunohistochemical and Biogenetic Features of Diffuse-Type Tenosynovial Giant Cell Tumors: The Potential Roles of Cyclin A, P53, and Deletion of 15q in Sarcomatous Transformation

Purpose: Diffuse-type tenosynovial giant cell tumor (D-TSGCT) is an aggressive proliferation of synovial-like mononuclear cells with inflammatory infiltrates. Despite the COL6A3-CSF1 gene fusion discovered in benign lesions, molecular aberrations of malignant D-TSGCTs remain unidentified. Experimental Design: We used fluorescent in situ hybridization and in situ hybridization to evaluate CSF1 translocation and mRNA expression in six malignant D-TSGCTs, which were further immunohistochemically compared with 24 benign cases for cell cycle regulators involving G1 phase and G1-S transition. Comparative genomic hybridization, real-time reverse transcription-PCR, and a combination of laser microdissection and sequencing were adopted to assess chromosomal imbalances, cyclin A expression, and TP53 gene, respectively. Results: Five of six malignant D-TSGCTs displayed CSF1 mRNA expression by in situ hybridization, despite only one having CSF1 translocation. Cyclin A (P = 0.008) and P53 (P < 0.001) could distinguish malignant from benign lesions without overlaps in labeling indices. Cyclin A transcripts were more abundant in malignant D-TSGCTs (P < 0.001). All malignant cases revealed a wild-type TP53 gene, which was validated by an antibody specifically against wild-type P53 protein. Chromosomal imbalances were only detected in malignant D-TSGCTs, with DNA losses predominating over gains. Notably, −15q was recurrently identified in five malignant D-TSGCTs, four of which showed a minimal overlapping deletion at 15q22-24. Conclusions: Deregulated CFS1 overexpression is frequent in malignant D-TSGCTs. The sarcomatous transformation involves aberrations of cyclin A, P53, and chromosome arm 15q. Cyclin A mRNA is up-regulated in malignant D-TSGCTs. Non–random losses at 15q22-24 suggest candidate tumor suppressor gene(s) in this region. However, P53 overexpression is likely caused by alternative mechanisms rather than mutations in hotspot exons.

BCOR-CCNB3-positive soft tissue sarcoma with round-cell and spindle-cell histology: a series of four cases highlighting the pitfall of mimicking poorly differentiated synovial sarcoma.

BCOR–CCNB3 sarcoma is a genetically defined undifferentiated malignancy with Ewing sarcoma (ES)‐like round cells, and preferentially affects the bones of male adolescents. Sarcomas harbouring BCOR–CCNB3 rarely arise from soft tissues; therefore, we aimed to report four cases to expand the clinicopathological spectrum.