Chromosome 8p11.2 translocations: prevalence, FISH analysis for FGFR1 and MYST3, and clinicopathologic correlates in a consecutive cohort of 13 cases from a single institution.

Chromosome 8p11.2 translocations result in diverse oncogenic fusion genes involving FGFR1 or MYST3. Among 24,262 unique patient cytogenetic studies performed at the Mayo Clinic, 8p11.2 translocations were identified in 14 cases ( approximately 0.06%). FISH analysis was performed in 13 patients (12 had myeloid neoplasms) and revealed abnormalities of MYST3 (n = 4) or FGFR1 (n = 4) in eight patients. MYST3 abnormalities were associated with acute myeloid leukemia (AML), M4 in three and M6 in one. Three of the four FGFR1-rearranged cases were associated with myeloproliferative neoplasms but none, including the two with sole 8p11.2, displayed the typical phenotype for stem cell leukemia/lymphoma (SCLL) and only one had eosinophilia; the fourth case had AML-M4. FISH did not reveal FGFR1 involvement in the one patient with SCLL. We conclude that neither the SCLL phenotype nor blood eosinophilia is a consistent feature of FGFR1-associated 8p11.2 translocations; conversely, FISH might not always reveal FGFR1 involvement in typical SCLL.

Development of five dual-color, double-fusion fluorescence in situ hybridization assays for the detection of common MLL translocation partners.

Chromosomal rearrangements involving the mixed lineage leukemia (MLL) gene at 11q23 are frequent in adult and childhood acute leukemia and have been associated with an unfavorable prognosis. Recent evidence suggests that MLL gene partners may influence prognosis. Five translocations account for approximately 80% of MLL rearrangements: t(4;11)(q21;q23), AFF1/MLL; t(6;11)(q27;q23), MLLT4/MLL; t(9;11)(p22;q23), MLLT3/MLL; t(11;19)(q23;p13.1), MLL/ELL; and t(11;19)(q23;p13.3), MLL/MLLT1. We have designed dual-color, double-fusion fluorescence in situ hybridization (D-FISH) probe sets to identify these translocations. A blinded study was performed for each probe set using 25 normal bone marrow samples, 25 t(4;11), 20 t(6;11), 20 t(9;11), 18 t(11;19p13.1), and 20 t(11;19p13.3) leukemia specimens as defined by chromosome analysis. The findings demonstrated abnormal D-FISH results for 24 of 25 AFF1/MLL, 19 of 20 MLLT4/MLL, all 20 MLLT3/MLL, all 18 MLL/ELL, and all 20 MLL/MLLT1 samples, confirming the efficacy of these D-FISH assays in detecting these common MLL/partner translocations. Our D-FISH assays were more accurate than chromosome analysis at distinguishing disruption of 19p13.1/ELL from that of 19p13.3/MLLT1. We also demonstrated a statistically significant increase in complex/unbalanced MLL/partner translocations occurring in pediatric patients versus adult patients (P = 0.02). A normal cutoff of 0.6% was established, suggesting an application for these assays in minimal residual disease detection and disease monitoring.

Fluorescence in situ hybridization to visualize genetic abnormalities in interphase cells of acinar cell carcinoma, ductal adenocarcinoma, and islet cell carcinoma of the pancreas.

OBJECTIVE: To use fluorescence in situ hybridization (FISH) to visualize genetic abnormalities in interphase cell nuclei (interphase FISH) of acinar cell carcinoma, ductal adenocarcinoma, and islet cell carcinoma of the pancreas. PATIENTS AND METHODS: Between April 4, 2007, and December 4, 2008, interphase FISH was used to study paraffin-embedded preparations of tissue obtained from 18 patients listed in the Mayo Clinic Biospecimen Resource for Pancreas Research with a confirmed diagnosis of acinar cell carcinoma, ductal adenocarcinoma, islet cell carcinoma, or pancreas without evidence of neoplasia. FISH probes were used for chromosome loci of APC (see glossary at end of article for expansion of all gene symbols), BRCA2, CTNNB1, EGFR, ERBB2, CDKN2A, TP53, TYMP, and TYMS. These FISH probes were used with control probes to distinguish among various kinds of chromosome abnormalities of number and structure. RESULTS: FISH abnormalities were observed in 12 (80%) of 15 patients with pancreatic cancer: 5 of 5 patients with acinar cell carcinoma, 5 of 5 patients with ductal adenocarcinoma, and 2 (40%) of 5 patients with islet cell carcinoma. All 3 specimens of pancreatic tissue without neoplasia had normal FISH results. Gains of CTNNB1 due to trisomy 3 occurred in each tumor with acinar cell carcinoma but in none of the other tumors in this study. FISH abnormalities of all other cancer genes studied were observed in all forms of pancreatic tumors in this investigation. CONCLUSION: FISH abnormalities of CTNNB1 due to trisomy 3 were observed only in acinar cell carcinoma. FISH abnormalities of genes implicated in familial cancer, tumor progression, and the 5-fluorouracil pathway were common but were not associated with specific types of pancreatic cancer.

Mosaic ring 20 with no detectable deletion by FISH analysis: Characteristic seizure disorder and literature review.

Ring chromosome 20 is a rare chromosome disorder characterized by a typical seizure phenotype consisting of complex partial seizures, frequent progression to generalized tonic or tonic-clonic seizures, and nocturnal frontal lobe seizures with frequent episodes of non-convulsive status epilepticus. Development may be normal or mildly delayed, followed by cognitive and behavioral decline after seizure onset. Here, we describe a patient with a typical severe seizure phenotype and a mosaic ring chromosome 20 without loss of p or q subtelomere regions or telomeric sequences. The ring had a longer telomere length than either of the telomere ends of its homologous chromosome 20 by quantitative fluorescence in situ hybridization analysis, suggesting that it might be derived from telomere-telomere fusion. The phenotypic comparison of this patient and other chromosome 20 cases that had terminal deletions of 20qter (n = 1) and 20pter (n = 7), shows that the epilepsy phenotype and electroencephalographic abnormalities are characteristic in patients with ring chromosome 20. Several hypotheses have been proposed to address the elusive mechanisms underlying the seizure disorder in ring chromosome 20. These possibilities include haploinsufficiency of two epilepsy genes CHRNA4 and KCNQ2 located at 20qter, silencing of these genes by a telomere position effect, or microdeletions or rearrangements of genetic material during the ring formation.