Phyllodes tumor of the breast with actin inclusions in stromal cells: diagnosis by fine-needle aspiration cytology.

The occurrence of hyaline inclusions in stromal cells in fibroepithelial tumors of the breast is very uncommon. These inclusions, characteristic of infantile digital fibromatosis, are comprised of actin filaments. This report illustrates a case of a benign phyllodes tumor of the breast with inclusion bodies, identified by fine-needle aspiration. Histologically, many of the stromal cells contained round intracytoplasmic inclusions, with positivity for smooth muscle actin. Copyright 2001 Wiley-Liss, Inc.