There are additional alterations in RET/PTC-positive tumours, which may act as modifiers of RET activation.     ///    "In contrast, alterations in RET/PTC-negative tumours indicate alternative routes of tumour development. "    ///    "In addition, childhood and adult RET/PTC-positive cases differ significantly for a deletion on the distal part of chromosome 1p. "    ///    "Specific aberration signatures were identified that discriminated between RET/PTC-positive and RET/PTC-negative cases (aberrations on chromosomes 1p, 3q, 4p, 7p, 9p/q, 10q, 12q, 13q and 21q). "    ///    Deletions were found more frequently in RET/PTC-positive and RET/PTC-negative tumours than amplifications.     ///    Array CGH demonstrates characteristic aberration signatures in human papillary thyroid carcinomas governed by RET/PTC..     ///    "We applied array-based comparative genomic hybridization (array CGH) to 33 PTC (20 PTC from adults, 13 post-Chernobyl PTC from children) with known RET/PTC status. "