OBJECTIVETo investigate the molecular genetic abnormalities of N-myc and C-myc, and their clinical pathological implications in pediatric neuroblastic tumors (NTs).

METHODSAbnormalities of N-myc were detected by interphase fluorescence in situ hybridization (FISH) technique in 246 cases of NTs, including neuroblastoma (NB,188 cases), ganglioneuroblastoma (GNB, 52 cases), ganglioneuroma (GN, 6 cases), and their association with the histological typing of the tumors and prognosis was analyzed. Abnormalities of C-myc were detected by FISH in 133 cases of NTs.

RESULTSOf the 246 cases of NTs, N-myc amplification was only found in 27 cases (11.0%, 27/246) of NB, but not in any cases of GNB or GN (P < 0.05). 89.0% (219/246) N-myc non-amplification were found in NTs, and it included N-myc gain in 175 cases (71.1%, 175/246) and normal N-myc in 44 cases (17.9%, 44/246). Univariate analysis indicated significantly (P = 0.012) poorer outcome in patients with N-myc amplification than N-myc non-amplification. However no significant difference was observed between N-myc gain cases and normal N-myc cases (P = 0.057). C-myc gain was found in 74 of 133 cases (55.6%) of NTs; no C-myc amplification or translocation was detected. Forty percent (6/15) of cases with N-myc amplification and 57.6% (68/118) of cases with N-myc non-amplification were accompanied by C-myc gain. The difference between N-myc amplification and non-amplification with C-myc gain was not significant (P > 0.05). Univariate analysis indicated that the outcome difference was not statistically significant between C-myc gain cases and normal C-myc cases (P = 0.357).

CONCLUSIONSThe incidence of N-myc amplification only found in NB is low in pediatric NTs in China. Patients with N-myc amplification predict poorer outcome. No amplification or translocation of C-myc is detected in NTs, whereas C-myc gain is relatively common in NTs. There is no obvious association between N-myc amplification and C-myc gain.