TY - JOUR TI - Myofibroblastoma of the breast: Cytologic, histologic, immunohistochemical, and ultrastructural findings in two cases with differing cellularity AU - Deligeorgi-Politi, H. AU - Kontozoglou, T. AU - Joseph, M. AU - Hearn, S. JO - The Breast Journal PY - 1997 VL - 3 TODO - 6 SP - 365-371 PB - Blackwell Publishing Inc. SN - 1075-122X, 1524-4741 TODO - 10.1111/j.1524-4741.1997.tb00195.x TODO - CD34 antigen; estrogen receptor; progesterone receptor, adult; aged; article; aspiration biopsy; breast biopsy; breast disease; breast tumor; case report; cell ultrastructure; differential diagnosis; electron microscopy; female; human; human cell; human tissue; immunohistochemistry; male; myofibroblast; tumor diagnosis TODO - We present the cytologic, histologic, immunohistochemical, and ultrastructural features of two cases of myofibroblastoma with different cellularity, one paucicellular the other hypercellular. Fine-needle aspiration suggested the diagnosis in the case of the hypercellular tumor of the breast and pointed out the benign nature of the paucicellular case, arising in the breast of a young woman. Immunohistochemistry, showed smooth muscle-specific actin, vimentin, and desmin positivity consistent with myofibroblastic differentiation, in both cases. The positivity of both tumors to CD34 suggests that they may be related to the so-called solitary fibrous tumor. In addition, there was strong progesterone- and weak estrogen-receptor positivity ion the hypercellular case, a novel finding in these tumors, with possible histogenetic implications. Ultrastructural findings in the first case were consistent with the myofibroblastic origin of the tumor. ER -