DISCRIMINATION BETWEEN MULTICENTRIC AND MULTIFOCAL BREAST-CARCINOMA BY CYTOGENETIC INVESTIGATION OF MACROSCOPICALLY DISTINCT IPSILATERAL LESIONS

Whether macroscopically distinct carcinomas in the same breast are clo nally related (multifocal breast carcinoma) or unrelated (multicentric breast carcinoma) is no longer only a scientific-pathological issue b ut, because different therapeutic strategies may be preferable for cas es with intramammary metastatic disease compared with cases of multipl e primary breast carcinomas, one that may have profound clinical impli cations. We studied the evolutionary relationship among macroscopicall y distinct, ipsilateral breast carcinomas by cytogenetic analysis of 2 6 tumorous lesions from 12 patients. Sixteen of the 26 foci (62%) were found to contain clonal chromosome abnormalities. Two carcinoma foci were karyotypically abnormal in each of seven patients. Four of these cases had an evolutionarily related, cytogenetically abnormal clone in the two lesions from the same breast, whereas the remaining three cas es had completely different clonal karyotypic aberrations in the separ ate foci. These results, together with our previous findings in five o ther informative cases, show that multiple, synchronous breast tumors sometimes arise through intramammary spreading of a single primary car cinoma, whereas on other occasions they are the result of the simultan eous emergence of pathogenetically independent carcinomas within the b reast. In the total material, an association was seen between the prox imity of the foci and the likelihood of them being karyotypically rela ted. (C) 1997 Wiley-Liss, Inc.