CD34+ fibrocytes are preserved in most invasive lobular carcinomas of the breast.

It is generally agreed that invasive carcinomas of the breast consistently lack stromal CD34+ fibrocytes. The pertinent literature shows that this assumption is well based for invasive ductal carcinomas, but evidence of loss of stromal CD34+ cells in lobular carcinomas is weak. We present a series of 22 invasive lobular carcinomas (ILCs) which, in contrast to invasive ductal carcinomas, display a gradual reduction of stromal CD34+ fibrocytes. One third of the study population showed a completely preserved population of CD34+ fibrocytes, in another third, this cell population was reduced in comparison to normal breast tissue, and in the remaining third, loss of CD34+ fibrocytes comparable to that occurring in virtually all invasive ductal carcinomas was found. The present study shows that loss of CD34+ fibrocytes is not a consistent feature of invasive carcinomas of the breast. Therefore, a preserved CD34+ stromal cell population does not exclude malignancy, and analysis of the stromal CD34 expression should be handled with care when used as a diagnostic tool.