Papillary neoplasms of breast constitute a group of lesions that show broad spectrum of morphological changes, ranging from benign to malignant and posing challenges at all diagnostic levels. Some benign papillary lesions may form well-defined solid masses with a dominant sclerosed architecture, known as complex sclerosing papillary lesion or simply sclerosing papilloma. The purpose of this study is to apply the previously published criteria for papillary lesions and to identify the cytomorphologic findings that lead to false-positive diagnosis of these cases. We reviewed the fine needle aspiration biopsies (FNAB) of six histologically proven sclerosing papilloma that were called suspicious or malignant on FNAB. The patient age ranged from 40 to 69, with a mean of (43 ± 6) yr. Three patients presented with a palpable lump and two patients had history of fibrocystic disease. All six patients had abnormal screening mammograms. FNAB was performed using a 23-gauge syringe attached to a commercial holder. FNA smears were markedly hypercellular with large number of epithelial fragments and papillary clusters, discohesive single cells that are hyperchromatic with mild to moderate nuclear pleomorphism. Bipolar cells were present in all cases, varying from low to abundant. Intraoperative consultation was requested on four cases. Touch preparations were made on two cases and were reported as suspicious based on the cellularity and nuclear atypia. All surgically excised specimens showed sclerosing complex papillary proliferative lesions with epithelial hyperplasia. In conclusion, FNA cytology of this proliferative lesions may be highly cellular and may display cellular atypia similar to breast carcinoma and thus leads to false-positive interpretation. Diagn. Cytopathol. 2006; 34:114–118. © 2006 Wiley-Liss, Inc.