The recognized hyperplasia-atypia-carcinoma spectrum of histologic changes within columnar cell lesions and its frequent presence adjacent to more severe lesions like tubular carcinoma implies an association of progression to atypia/carcinoma [1
]. Columnar cell lesions with atypia (flat epithelial atypia, atypical ductal hyperplasia) are considered a “step behind” in the progression to ductal carcinoma in situ (DCIS). Molecular studies have corroborated that columnar cell lesions share similar genetic alterations as invasive breast carcinomas, such as LOH (loss of heterozygosity) at 11q21–23.2, 16q23.1–24.2 and 3p14.2 [4
]. Dabbs et al demonstrated allelic loss damage in columnar cell change, with preferentially targeted loci at 9q, 10q, 17p, and 17q, consistent with the hypothesis that a select group of atypical columnar cell lesions are very early precursors to invasive breast carcinoma [1
]. Columnar cell lesions should therefore be considered clonal and neoplastic
rather than a hyperplastic proliferation [1
PASH is considered to be “benign” or “hamartomatous” by some [10
], and neoplastic process by others due to its frequency of presentation, multifocality, and its potential to recur [13
Stromal microenvironment is necessary for normal mammary tissue development and breast cancer tumorigenesis. This is shown most strikingly in orthotopic transplants of normal human mammary epithelial cells (MEC) into the mouse mammary fat pad. Human MEC fail to develop into normal mammary structures when injected into mouse mammary fat pads. However, the presence of human stromal cells created an environment permissive for normal ductal development and function [7
]. Similar epithelial-stromal interaction influenced by some hormonal and angiogenic factors were observed by our group in CCPLS, further demonstrated by immunohistochemical stains.
Our CCPLS and PASH cases expressed AR, ER-beta and PR; therefore we raise the possibility that these proliferating ducts have the capacity to induce hormones in the surrounding stroma as well. Investigations on embryonic mouse mammary epithelium rudiments demonstrate their capacity to induce AR in the adjacent stroma, which is normally AR negative. Thus, as the breast tissue differentiates the mammary ducts are surrounded by AR positive stroma, as seen in our cases as well [16
Angiogenesis is an important component of tumorigenesis. CD105 (endoglin) is a 95 kD cell surface protein that functions as an endothelial marker and an accessory receptor for TGF-β [17
]. CD105 is expressed in endothelial cells, activated monocytes, differentiated macrophages and fibroblasts among other cells.It has been found to be up-regulated in tumor endothelial cells of breast and shown to be a useful marker of neoangiogenesis in this neoplasm [17
]. Studies have demonstrated that hypoxia, which is a common feature of proliferative lesions as tumors, is a potent stimulator of CD105 gene expression in vascular endothelial cells, and this effect can be potentiated by the presence of TGF-β. Expression of CD105 in these tumors correlates with vascular density and, most importantly, poor prognosis [5
]. In our cases, CD105 staining demonstrated significantly increased numbers of small-activated vessels in CCPLS. In contrast, TDLU and PASH show a lesser number of vessels. Through these observations we question if columnar cell epithelium is responsible for angiogenesis within the stroma of CCPLS, in turn a demonstration of epithelial-stromal interaction (Figure 9). Many of our CCPLS cases were Magnetic Resonance Imaging (MRI) guided core biopsies. Since this is a modality that detects vascular aberrations in the breast, it further supports our observations of angiogenesis associated with these lesions.
A strong expression of bFGF in CCPLS is also indicative of the vascular nature of these lesions. bFGF is a fibroblastic marker, demonstrated by expression in our PASH cases. The lack of immunostaining for bFGF in the stroma immediately surrounding breast epithelium suggests that this epithelium modulates the function of the stroma cells, dampening their bFGF production, which we described histologically as “halo effect”. This may represent an important endogenous mechanism of tumor suppression. The lack of bFGF in the immediate vicinity of potentially malignant epithelium may inhibit the angiogenesis necessary for the survival of these tumors ().
CD34, a marker of hematopoietic progenitor cells in the bone marrow, stains a variety of tissues [20
]. CD34 highlighted the myofibroblastic differentiation in CCPLS cases. MIB-1 was variably positive, and we agree with other studies that columnar cell lesions do not display high proliferation [23
], although CCPLS stroma can be slightly more proliferative than the normal TDLU ( and ).
C-kit (CD117) is a receptor-tyrosine kinase that is structurally similar to platelet derived growth factor and colony stimulating growth factor-1 [24
]. C-kit signaling promotes cell survival, cell differentiation, adhesion and chemotaxis [24
]. Expression of c-kit has been reported in both normal and neoplastic breast epithelium, and the results are quite variable. In most studies c-kit expression in breast carcinomas is shown in less than 20% of cases [25
], although the range is vast (1%-82% of cases) [24
], attributed to different methodologies for its detection. Loss of c-kit expression has been associated with increased numbers of lymph nodes involved by metastatic carcinoma, suggesting prognostic implications for this marker in breast carcinomas [24
]. Only one case of CCPLS demonstrated weak positivity for this marker in the stroma. We observed a reduced expression of c-kit in columnar cell lesions in comparison to stronger expression in TDLU. To our knowledge, our study is the first to report c-kit expression in columnar cell lesions. Our observations might represent a downregulation of c-kit protein expression corresponding with the “early precursor” nature of these lesions. Definitively, c-kit is of interest and future studies are needed to confirm its prognostic implications and possible therapeutic effects in these aggressive neoplasms ().
In conclusion, we have verified the presence of an epithelial-stromal interaction in CCPLS. The presence of hormonal and angiogenic factors in our cases of CCPLS is a good example of demonstration of epithelial-stromal interactions. Future studies with larger number of cases are needed to evaluate the significance of these factors and possible prognostic and therapeutic implications. The decreased expression of c-kit in columnar cell lesions is an interesting finding in our study, which needs to be further evaluated. Due to the small number of cases in our study no meaningful statistical analysis could be obtained. Though our study does not reflect a diagnostic utility, it emphasizes an observation of epithelial-stromal interaction in early preneoplastic lesions of the breast.