Cytological and histopathological features of two cases of intraductal papilloma of the breast judged to be malignant by fine-needle aspiration cytology

Abstract

Background : Difficulties diagnosing adenomyoepitheliomas of the breast based on fine-needle aspiration cytology have often been reported. Similar false-positive results may occur for intraductal papillomas of the breast that demonstrate prominent myoepithelial proliferation.
Case : We report the cytological and histopathological features of two cases of intraductal papilloma of the breast judged to be malignant (ductal carcinoma) based on fine-needle aspiration cytology. Cytologically, the presence of atypical cells with loose cellular adhesions and isolated atypical cells led to the diagnosis of malignant (ductal carcinoma) in both cases. A partial mastectomy was performed in both cases, with histopathological and immunohistochemical findings of the surgical specimens showing that both tumors were intraductal papillomas with prominent myoepithelial proliferation.
Conclusion : Proliferating myoepithelial cells can be present as atypical cells with loose cellular adhesions that mimic ductal carcinoma cells. The cytological characteristics of proliferating myoepithelial cells that may be helpful for differentiating them from ductal carcinoma cells include 1) a low N/C ratio, 2) a fine granular chromatin pattern, and 3) intranuclear inclusions.