Periductal stromal tumor

Fibroadenomas and phyllodes tumors comprise the vast majority of fibroepithelial tumors of the breast, though mammary hamartomas and periductal stromal tumor are also considered in this category. 

Periductal stromal tumor was initially described by Burga and Tavassoli as a distinct entity from phyllodes tumors that was histologically identical but lacked the intracanalicular or leaflike pattern.Like phyllodes tumors, however, the stromal cells express CDS 4, and thus some have proposed that they are best regarded as a phyllodes tumor variant that lacks the classic leaflike architecture rather than a distinct entity. 

Periductal stromal tumor is likely a variant of phyllodes tumor it also has a CD34-positive stroma. 

Burga AM, Tavassoli FA. Periductal stromal tumor A rare lesion with low-grade sarcomatous behavior. Am J Surg Pathol. 2003 27 343-348. 

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