Multicenter standardization study may accelerate the implementation of ALK testing protocols across a country/region. Our data support the use of an appropriately validated IHC assay to screen for ALK+ lung cancers.

A novel in situ hybridization technique is described. This non-radioactive technique combines, for the first time, the high spacial resolution and rapid signal development of the non-isotopic approach with the previously unrivalled sensitivity of autoradiography. The procedure, which employs biotin labelled DNA probes and a streptavidin-alkaline phosphatase based detection system, is compatible with pre G-banding and can be performed on archival material. Unique sequences as small as 1 Kb are detectable. Using this technique, we have mapped the N-myc oncogene and the gene for beta-Nerve Growth Factor to 2p24 and 1p13 respectively.

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Sixty spare human embryos at various stages of preimplantation development were prepared for cytogenetic analysis. Fluorescent staining of those with metaphases allowed scoring for the presence of a Y chromosome. In situ hybridization was then performed using a biotinylated Y-specific sequence, and the probe was detected by a standard streptavidin-linked alkaline phosphatase system. This enabled comparison of the chromosomal sex with that obtained after in situ hybridization in 28 embryos, and the sexing result obtained by the two methods was concordant in all cases. A further 21 embryos in which no metaphase chromosomes were obtained were sexed by biotinylated in situ hybridization only. Overall, 66 per cent of male interphase nuclei demonstrated a Y-specific hybridization signal. Results were obtained in under 24 h, which may permit the sexing of an embryo biopsied during cleavage and the transfer of sexed embryos at the blastocyst stage to the mother's uterus in the same cycle as oocytes are collected for in vitro fertilization.

Gene amplification in mammalian cells commonly manifests itself as homogeneously staining chromosomal regions (HSRs). These are frequently seen in neuroblastoma and have been shown to be the site of amplification of the NMYC oncogene. We have used a nonisotopic, high-resolution in situ hybridization technique to reveal a hitherto unrecognized periodic microstructure within HSRs of a human neuroblastoma cell line.