Periductal Stromal Tumor of the Breast: Case Report and Literature Review.

Periductal stromal hyperplasia is an exceedingly rare biphasic breast tumor with benign ductal elements and spindle-cell stromal proliferation lacking a phyllodes architecture. It is unclear whether this tumor belongs to the spectrum of phyllodes tumor or is a separate entity. We present a 57-year-old woman with a 3.0×2.3×1.0 cm lesion in the left breast. Sections of the excision specimen showed nodular hypercellular spindle cell proliferation with ductal centric arrangement and infiltration into the adipose tissue. The spindle cells showed bland nuclei, no visible mitoses, no leaflike growth pattern, and low Ki-67(<1%). Spindle cells were positive for CD34, and negative for SMA, myosin, CD117, and beta-catenin. Presentation of this case helps in further defining the clinical, histopathologic, management and outcome of this tumor.