Highly recurrent der(1;16)(q10;p10) and other 16q arm alterations in lobular breast cancer.

Cytogenetic data on infiltrating lobular carcinomas (ILCs) of the breast are described. In addition to 9 tumors, including 2 bilateral ones, with apparently normal chromosomes, recurrent chromosome alterations were found among 18 tumors. A der(1;16)(q10;p10), resulting in 1q gain and 16q loss, was observed in 11 tumors. Chromosome arm 16q was lost by other rearrangements in 3 other tumors. Thus, the deletion of 16q appears to be highly recurrent in ILCs. Compared to infiltrating ductal carcinomas (IDCs), ILCs have fairly simple karyotypes that remain pseudo- or near-diploid in most cases. This finding is confirmed by DNA ploidy studied by flow cytometry, which shows that about half of the tumors are diploid. This makes the der(1;16)(q10;p10) and other alterations of the 16q arm an early alteration of tumor progression, possibly related to the loss of expression of E-cadherin, whose gene is mapped on the 16q arm.