Cytogenetic analyses of secondary liver tumors reveal significant differences in genomic imbalances between primary and metastatic colon carcinomas

To investigate if karyotypic features of secondary liver tumors may provide diagnostic information and if the cytogenetic patterns of primary and meta static colorectal carcinomas (CRC) are different, 33 liver metastases were analyzed: 25 CRC, 4 small intestine carcinoids, 1 ovarian carcinoid, 1 lobu lar breast cancer, 1 head-and-neck squamous cell carcinoma, and 1 uveal mal ignant melanoma. Chromosomal aberrations were detected in 24 cases, whereas 5 had normal karyotypes and 4 were uninformative due to lack of mitoses. T risomy 12 was detected in 2 small intestine carcinoids, suggesting that +12 may be of pathogenetic importance in this tumor type. The breast and head- and-neck carcinomas and the uveal melanoma displayed aberrations previously reported as characteristic in primary tumors, e.g., der(1;16) and deletion of 3p in the breast cancer, losses of 3p and 8p and partial gain of 8q in the head-and-neck carcinoma, and monosomy 3 and i(8)(q10) in the uveal mela noma, indicating that cytogenetic investigations provide important diagnost ic information in secondary liver tumors. In the 18 CRC metastases with chr omosomal abnormalities, the cytogenetic findings agreed well with previousl y reported primary CRC. Common numerical abnormalities included gains of ch romosomes 7, 11, 13, and 20, and losses of Y, 4, 18, 21, and 22. Structural rearrangements most often affected chromosome bands 1p13, 1q10, 3p21, 5q10 , 5q11, 7q10, 8q10, 8q11, 12q13, 16p13, 17p11, 20p13, 20p11, and 20q10, and frequently resulted in losses of 1p, 8p, and 17p, and gains of 5p, 6p, 7p, 8q, and 20q. Comparing the present cases with primary CRC previously analy zed in our department revealed that additional gains of 6p, 6q, 7p, and 20q , and losses of 1p, 4p, 4q, 8p, 18p, 18q, and 22 were more common (P < 0.05 ) in the metastases, suggesting that these genomic sites harbor genes of im portance in the metastatic process of CRC.