Fine needle aspiration of spindle cell ductal carcinoma in situ of the breast: A case report and the use of ancillary tests for the differential diagnosis of metaplastic carcinoma

Spindle cell ductal carcinoma in situ (DCIS) is a recently recognized subtype of DCIS, which is associated with a very rare and unique morphology. Although the histologic features have been relatively well described in a few reports, the cytologic features have not. Even though the distinction of this lesion from usual DCIS is not crucial clinically, it should be noted that this lesion might simulate the features of metaplastic carcinoma on fine needle aspiration cytology. Here, we report a case of spindle cell DCIS in a 45-year-old female, with the detailed cytologic features, both on conventional and liquid-based preparations, along with some useful immunohistochemical staining markers for the differential diagnosis.