Differential cytologic features of fibroepithelial lesions of the breast.

The surgical treatment of phyllodes tumors differs from that for fibroadenomas, with the former necessitating complete excision with no remaining neoplastic tissue to produce local recurrence. To determine whether we could predict the type of breast lesion on cytology we reviewed the cytological features of 39 fibroepithelial lesions, including ordinary fibroadenomas, fibroadenoma variants (intermediate group), benign phyllodes tumors, and malignant phyllodes tumors, which had a biopsy diagnosis and adequate cytology. We found no differences in the glandular elements, the myoepithelial and single stromal cells, and the type of stromal fragments seen in the three benign groups. The stromal nuclei, the number of leaf-shaped fragments, and the numbers of spindle-cell groups present showed a spectrum of changes varying from those of fibroadenomas at one end to those of benign phyllodes tumors at the other. Malignant phyllodes tumors had characteristic features which were quite different from those of the benign lesions.