FLUORESCENCE IN-SITU HYBRIDIZATION (FISH) DETECTION OF MYCN ONCOGENE AMPLIFICATION IN NEUROBLASTOMA USING PARAFFIN-EMBEDDED TISSUES

The expression and degree of amplification of the MYCN oncogene in neu roblastoma provide an important indicator of disease prognosis. Detect ion of MYCN amplification has been described using Southern blotting o r polymerase chain reaction (PCR) on DNA from fresh or frozen tissue s amples, and using in situ hybridization mainly on metaphase spreads or smears of cultured neuroblastoma cells. In this article, we describe fluorescence in situ hybridization (FISH) results on detection of MYCN amplification in formalin-fixed, paraffin-embedded samples of 25 neur oblastoma and 20 nonneuroblastoma pediatric tumors. MYCN amplification was readily detectable by FISH in eight of the neuroblastomas; correl ation with results obtained by Southern analysis was perfect. Of the n onneuroblastoma tumors, only one of three retinoblastoma cases showed MYCN amplification. In contrast to the Southern blot technique, FISH d emonstrated the state of amplification heterogeneity of the tumor cell s as well as the nature of the amplification units: double-minute chro mosomes (DMs) or homogeneously staining regions (HSRs). The results in dicate that FISH is a rapid and reliable method for detection of MYCN oncogene amplification in routinely processed samples and may be used to supplant the Southern blot technique.