CYTOGENETIC ANALYSIS SHOWS THAT CARCINOSARCOMAS OF THE BREAST ARE OF MONOCLONAL ORIGIN

Carcinosarcoma of the breast is a rare biphasic neoplasm composed of a carcinomatous component contiguous or admired with a pleomorphic spin dle cell component. The issues of the histogenesis and clonal composit ion of carcinosarcomas have long been debated. We present the first cy togenetic characterization of mammary carcinosarcomas by analysis of e ight tumor samples from two patients with this disease. In the first c ase, the same karyotypically complex clone, as well as evidence of clo nal evolution, was found in samples from three separate areas of the p rimary tumor. The analysis of one intramammary and one axillary lymph node metastasis from the same patient, both showing only the sarcomato us tumor component, also revealed the common complex stemline and one of the two sidelines found in the primary tumor. The carcinosarcoma of the second patient contained six complex but karyotypically related c lones unevenly distributed among the three samples examined. From this case, cells belonging to the carcinomatous and sarcomatous tumor comp onents were separated by differential sedimentation and culturing in s pecific growth media. Analysis of both fractions showed largely the sa me karyotype, although one of the subclones was restricted to the epit helial component. Our findings indicate that the epithelial and mesenc hymal components of mammary carcinosarcomas are both part of the neopl astic parenchyma and that they have evolved from a single common stem cell, in agreement with the hypothesis that the tumors are of monoclon al origin. (C) 1998 Wiley-Liss, Inc.