Preoperative Discrimination of Fibroadenoma Which Is Clinically and Cytologically Indistinguishable from Breast Carcinoma through Clonal Analysis of Fine Needle Aspirate of Tumor: Report of a Case.

Recently, it has been demonstrated that breast carcimoma is monoclonal and fibroadenoma is polyclonal in origin. In the present case report, this observation was successfully applied to a preoperative differential diagnosis of a fibroadenoma clinically and cytologically indistinguishable from carcimoma. Case report: A45-year old female presented for clinical examination with a history of breast lump. A firm tumor measuring 2 x 2 cm was palpable in the upper-outer quadrant of @the left breast. The margin of the tumor was partially ill-defined and its mobility was restricted. A tumor shadow with a partially ill-defined margin was revealed by mammography. Ultrasonographic examination showed and irregularly-shaped, hypo-echoic tumor accompanied by an acoustic shadow. Fine needle aspiration biopsy yielded positive cytology. Based on these results, the tumor was diagnosed as breast carcinoma. However, clonal analysis of fine needle aspirates showed a polyclonal pattern, strongly indicating that the tumor was not a carcinoma but benign disease; most probably fibroadenoma. Thus, an open surgical biopsy was performed. Histoglogical examination revealed that the tumor was indeed a fibroadenoma with epithelial hyperplasia. This case suggests the usefulness of clonal analysis of fine needle aspirates in differentiating fibroadenoma from carcinoma of the breast.