PROGRESSION OF FIBROADENOMA TO PHYLLODES TUMOR DEMONSTRATED BY CLONALANALYSIS

Background. The histogeneses of fibroadenoma and phyllodes tumor of th e breast appear to be closely related, but it is still unclear whether fibroadenoma can progress directly to phyllodes tumor. Methods. This issue was studied by conducting clonal analysis of fibroadenoma and ph yllodes tumors that were obtained sequentially from the same patient. One patient developed local recurrence of phyllodes tumor twice, and t he other two patients each developed a phyllodes tumor after excision of a primary fibroadenoma. The method for clonal analysis was based on trinucleotide repeat polymorphism of the X chromosome-linked androgen receptor (AR) gene and on random inactivation of the gene by methylat ion. Results. Clonal analysis revealed that all the three primary fibr oadenomas were monoclonal and all four recurrent phyllodes tumors were also monoclonal in origin. In addition, the same allele of the AR gen e was inactivated in fibroadenoma and phyllodes tumor(s) in each patie nt. The probability that phyllodes tumors of different origin happen t o inactivate the same allele of the AR gene as fibroadenomas in every case is quite low. Rather, it is more reasonable to assume that the ph yllodes tumor has the same origin as fibroadenoma. Conclusions. These results identified monoclonal fibroadenomas that can progress to phyll odes tumors.