Phylloides tumor of the breast is well known entity in pathology for a long time. It includes fibroepithelial tumors of the different biological character. They are generally divided into three groups: benign, low-grade malignant (borderline) and high-grade malignant. Adenoses of the breast are a group of the benign lesions, the main feature of which is the proliferation of the glandular component of the breast. More frequent adenoses occurring in practice are: blunt duct adenosis, sclerosing adenosis, nodular adenosis, adenosis tumor and florid adenosis. The less frequent adenoses are: microglandular adenosis, tubular adenosis, apocrine adenosis, and myoepithelial (adenomyoepithelial) adenosis. In this article two histologically unusual lesions of the breast in middle-aged women are presented, consisting of the benign variants of the phylloides tumor, modified distinctly by various types of adenoses, which can cause, together with intensive myoepithelial proliferation, great diagnostic problems, especially on frozen sections. They may be mistaken with invasive ductal or lobular cancer. Reliable differentiation between these entities is possible only by using of the immunohistochemical methods.

        Key words: benign phylloides tumor of the breast - adenosis of the breast - myoepithelial proliferation - invasive carcinoma - frozen section - immunohistochemistry