Telocytes of the mammary gland stroma.

Although confusions persist in what concerns the terminologies used for describing the fibroblastoid cells of the stromal compartments, the expression of antigens in such cells gradually directs their diagnosis towards a stem/progenitor phenotype. The stromal cells with long, slender and moniliform prolongations were named “telocytes” (TCs), their cell processes being termed “telopodes”. However, the mammary gland TCs were not evaluated for the CD34 expression. Thus an in vivo immunohistochemical study was designed; antibodies against CD10, CD34, CD117/c-kit and vimentin were applied on human mammary gland samples of 8 donor patients. Resident CD34-positive stromal cells positive for the TCs morphology were found building consistent stromal networks and ensheathing microvessels and excretory units. Such cells were CD10±/c-kit-/vimentin+. According to the current concepts regarding the in vivo stem/progenitor cells the CD34+ TCs of the mammary stroma could be actors in the mammary stem niche and their antigens expression could relate to different stages of differentiation.