Numerical chromosome changes in thyroid cells from fine needle aspiration biopsy (FNAB).

It is now common knowledge that two types of genetic instability, microsatellite instabilty (13% of cancers) and chromosome instability (87% of cancers), substantially contribute to the sequential accumulation of genetic alterations leading to cancer. Aneuploidy, a mirror of chromosome instability, characterizes a subgroup of follicular thyroid lesions, often associated with oncocytic features, which show simple trisomy 7 or trisomy 7 accompained by additional polysomies, accumulating according to an evolutionary scheme which parallels the progression from hyperplasia to carcinoma. In order to: a) verify the possibility of recognizing numerical chromosome changes in thyroid cells prior to surgical resection, b) establish the frequency of nodules with numerical chromsome changes prior to surgery selection and c) to confirm the association between aneuploidy and mithocondria accumulation, cells from the thyroid nodules of 108 patients undergoing echo-guided FNAB were investigated, using Fluorescence in Situ Hybridization (FISH) with centromeric probes specific for chromosomes 7 and 17, and immunofluorescence and FISH (FICTION), using anti-mitochondrion antibody. Numerical chromosome changes for chromosome 7 and/or 17 were found in cells from 8 nodules (4 with oncocytic features), and chromosome 7 and 17 heterozygous centromeric fusion was observed in 1 nodule. All cytological specimens were classified as suspicious. Six of them were subsequently surgically removed (4 carcinomas, 2 adenomas) and chromosome changes were confirmed in nuclei from fresh (touch preparations) or fixed (paraffin embedded) surgical material of 5 cases. CONCLUSIONS. Our data demonstrate the possibilty of performing FISH and FICTION experiments on cells from FNAB material, indicate that 7.4% of nodules subjected to echo-guided FNAB were associated with numerical chromosome changes, and, finally, confirmed that trisomy 7 alone or accompained by other chromosomes gains is present in oncocytic cells. (The authors thank Prof. Mariano Rocchi for the centromeric probes. Partially supported by MURST and RAS).