A cytogenetic study of male breast cancer.

In a direct preparation from a male breast carcinoma two populations of cells were present, one hypodiploid (range 25-34) and the other hypertriploid (range 56-84). Twenty-two marker chromosomes were recognized. One of these, dic(5:11)(p14:q23) was present in one or two copies in every cell and has not been reported in any other case of breast cancer. There was a consistent monosomy of chromosome 7 and, in the hypertriploid cells, a gain of one to three copies of chromosome 3. The breakpoint 11q23 is a rare, folate-sensitive fragile site but was not expressed in peripheral blood cell lymphocytes from the patient.