Expression of c-kit in fibroepithelial lesions of the breast is a mast cell phenomenon

The Genetic Landscape of Fibroepithelial Lesions of the Breast

Fibroepithelial lesions of the breast encompass a broad spectrum of lesions from fibroadenomas and their variants to phyllodes tumors, including their clinical range of benign, borderline, and malignant. Classification of this spectrum of neoplasms has historically and currently been based purely on morphology, although the nomenclature has shifted over the years largely due to the significant histologic overlap that exists primarily within the cellular fibroadenomas to borderline malignant phyllodes tumor categories. A review of the current diagnostic challenge, proposed ancillary studied and their value in prognostic significance, is provided. This article highlights the most recent molecular and genetic findings as well as the limitations of the studies, in the context of practical and available applications for the diagnostician and managerial implications for the clinician.

Malignant transformation of phyllodes tumor: a case report and review of literature

Malignant phyllodes may transform from benign phyllodes; low-aggressive malignant phyllodes tumor is manageable by locally wide excision.

Molecular alterations in lesions of anogenital mammary-like glands and their mammary counterparts including hidradenoma papilliferum, intraductal papilloma, fibroadenoma and phyllodes tumor

Lesions affecting anogenital mammary-like glands (AGMLG) are histopathologically very similar to those seen in the breast but whether this morphological similarity is also reflected at the genetic level is unknown. To compare the underlying molecular mechanisms in lesions of AGMLG and their mammary counterparts, we analyzed the mutational profile of 16 anogenital neoplasms including 5 hidradenomas papilliferum (HP), 1 lesion with features of HP and fibroadenoma (FA), 7 FA, 3 phyllodes tumors (PhT)) and 18 analogous breast lesions (6 intraductal papillomas (IDP), 9 FA, and 3 PhT) by high-coverage next generation sequencing (NGS) using a panel comprising 50 cancer-related genes. Additionally, all cases were analyzed for the presence of a mutation in the MED12 gene. All detected mutations with allele frequencies over 20% were independently validated by Sanger sequencing (concordance: 100%). Mutations in PIK3CA, AKT1, MET, ABL1 and TP53 genes were found in lesions of AGMLG and also their mammary counterparts. The PI3K-AKT cascade plays a role in tumors arising at both sites. It appears that some histopathologically similar anogenital and breast lesions develop along similar molecular pathways.

Associations of epithelial c-kit expression in phyllodes tumours of the breast

BACKGROUND

Mammary phyllodes tumours (PT) are rare biphasic neoplasms but have important clinical significance. Both epithelial and stromal components participate in PT development. Despite a number of studies on stromal c-kit in PT, little is known about the role of its epithelial expression.

OBJECTIVE

To further evaluate the stromal and epithelial expression of c-kit in a cohort of patients with PT.

METHOD AND RESULTS

Expression of c-kit in both epithelial and stromal components was examined and correlated with histological features in PT. Stromal c-kit expression was associated positively with stromal cellularity (median expression=10.0, 30.0 and 50.0 from mild to severe cellularity; p=0.019). Conversely, a significant negative trend between epithelial c-kit expression with stromal pleomorphism (median expression=55.0, 30.0 and 2.5 from mild to severe pleomorphism; p=0.043) and mitosis (median expression=70.0 and 20.0 for low and high mitosis respectively; p=0.003); and a trend of negative correlation with increased PT grade was found. Despite these reverse associations, epithelial and stromal c-kit expressions were positively correlated with each other. Notably, the correlation of stromal c-kit expression with malignant histological features appeared to be stronger in cases with low epithelial c-kit expression but not in those with high epithelial c-kit expression.

CONCLUSIONS

This study demonstrated the association of epithelial c-kit expression with stromal histological features and stromal c-kit. Interestingly, epithelial c-kit expression affected the strength of the correlation of stromal c-kit with these histological features. These findings provide further evidence of the interaction between the epithelial and stromal components in PT.

CD117 expression in breast phyllodes tumors correlates with adverse pathologic parameters and reduced survival

CD117 (c-kit) is a type III receptor tyrosine kinase encoded by the KIT gene. Deregulation of expression and mutations in the gene are implicated in various tumors. Reports of CD117 expression in phyllodes tumors have been controversial. We aim to investigate the protein expression of CD117 and mutations in the KIT gene in phyllodes tumors, and correlate the findings with pathological parameters and clinical outcome. A total of 272 cases were included in this study. CD117 expression was investigated by immunohistochemistry on tissue microarray sections. Toluidine blue staining was performed to indicate mast cells. Overall, 28 (10%) cases were CD117 positive. CD117 expression was significantly associated with tumor grade (P<0.001), increased stromal hypercellularity (P=0.003), stromal atypia (P=0.01), and stromal mitotic activity (P<0.001), permeative microscopic margins (P=0.002), and presence of hemorrhage (P=0.001). Expression was also associated with poorer overall survival (P=0.003). Nineteen cases were further selected for mutation screening through the Affymetrix OncoScan platform. No mutation of the KIT gene was found. Despite a lack of mutations in the KIT gene, CD117 protein expression is associated with unfavorable pathological parameters and poorer prognosis, suggesting an underlying role in the biology of phyllodes tumors.

Fibroepithelial tumors of the breast: pathologic and immunohistochemical features and molecular mechanisms

CONTEXT

The 2 main prototypes of fibroepithelial tumors of the breast include fibroadenoma and phyllodes tumor (PT). Although both tumors share some overlapping histologic features, there are significant differences in their clinical behavior and management. Phyllodes tumors have been further divided into clinically relevant subtypes, and there is more than one classification scheme for PT currently in use, suggesting a lack of consistency within different practices. Accurate differentiation between fibroadenoma and PT, as well as the grading of PT, may sometimes be challenging on preoperative core needle biopsy. Some immunohistochemical markers have been suggested to aid in the pathologic classification of these lesions.

OBJECTIVE

To discuss the salient histopathologic features of fibroepithelial tumors and review the molecular pathways proposed for the initiation, progression, and metastasis of PTs. Also, to provide an update on immunohistochemical markers that may be useful in their differential diagnosis and outline the practice and experience at our institution from a pathologic perspective.

DATA SOURCES

Sources included published articles from peer-reviewed journals in PubMed (US National Library of Medicine).

CONCLUSIONS

Fibroepithelial tumor of the breast is a heterogenous group of lesions ranging from fibroadenoma at the benign end of the spectrum to malignant PT. There are overlapping histologic features among various subtypes, and transformation and progression to a more malignant phenotype may also occur. Given the significant clinical differences within various subtypes, accurate pathologic classification is important for appropriate management. Although some immunohistochemical markers may be useful in this differential diagnosis, histomorphology still remains the gold standard.

Utility of Ki-67, CD10, CD34, p53, CD117, and Mast Cell Content in the Differential Diagnosis of Cellular Fibroadenomas and in the Classification of Phyllodes Tumors of the Breast

Adequate management of phyllodes tumors of the breast (PTB) remains a challenge because of the difficulty in correctly establishing preoperative diagnosis. The aim of this study was to evaluate the usefulness of Ki-67, CD10, CD34, p53, CD117, and of the number of mast cells in the differential diagnosis of benign PTB and cellular fibroadenomas (CFs) as well as in the grading of PTB. Fifty-one primary PTB and 14 CFs were examined by immunohistochemistry.When evaluating CD117 expression, higher epithelial expression was present in CF as well as an increased number of mast cells in benign PTB. Stromal expression of Ki-67, CD10, CD34, and p53 were relevant to PTB grading, of which the first 3 showed significance in the distinction of benign and borderline PTB, as well as between benign and malignant PTB. P53 was relevant only for the discrimination between benign and malign PTB. None of the markers showed significance in distinguishing between borderline and malign PTB.

The significant role of mast cells in cancer

Mast cells (MC) are a bone marrow-derived, long-lived, heterogeneous cellular population that function both as positive and negative regulators of immune responses. They are arguably the most productive chemical factory in the body and influence other cells through both soluble mediators and cell-to-cell interaction. MC are commonly seen in various tumors and have been attributed alternatively with tumor rejection or tumor promotion. Tumor-infiltrating MC are derived both from sentinel and recruited progenitor cells. MC can directly influence tumor cell proliferation and invasion but also help tumors indirectly by organizing its microenvironment and modulating immune responses to tumor cells. Best known for orchestrating inflammation and angiogenesis, the role of MC in shaping adaptive immune responses has become a focus of recent investigations. MC mobilize T cells and antigen-presenting dendritic cells. They function as intermediaries in regulatory T cells (Treg)-induced tolerance but can also modify or reverse Treg-suppressive properties. The central role of MC in the control of innate and adaptive immunity endows them with the ability to tune the nature of host responses to cancer and ultimately influence the outcome of disease and fate of the cancer patient.

HESRG: a novel biomarker for intracranial germinoma and embryonal carcinoma

The novel stem cell-related gene, HESRG, was first identified by our group, and its expression pattern in human tumors remains unknown. In this study, we used RT-PCR to systematically investigate the expression of HESRG in various types of intracranial tumors and found that HESRG was expressed only in germinoma and embryonal carcinoma, but hardly at all in other types of brain tumors. Real-time PCR results further confirmed this expression pattern. Subsequently, we tested 134 intracranial non-germ cell tumors and 64 intracranial germ cell tumors by immunohistochemistry. Our results showed that HESRG was expressed strongly and diffusively in the nuclei of tumor cells in intracranial germinoma and embryonal carcinoma as well as in human embryonic stem cells. No positive staining signal was observed in any other type of intracranial tumors. In germinomas, 25 of 31 showed intensive (3+) expression, four cases showed moderate (2+) immunostaining and the remaining 2 cases showed weak (1+) immunostaining. In embryonal carcinoma, 6 of 9 showed intensive (3+) immunostaining and 3 of 9 showed moderate (2+) immunostaining. These results suggest that HESRG is a novel, sensitive and specific biomarker for intracranial germinoma and embryonal carcinoma.

CD117 is not a useful marker for diagnosing atypical fibroxanthoma

Atypical fibroxanthoma (AFX) is a rare skin tumor that generally pursues an indolent course despite its alarming histological appearances. It is important for the pathologist to distinguish this neoplasm from more aggressive lesions that may show very similar histological features. Recently, it has been suggested that demonstration of CD117 is of value in identifying AFX. To test this hypothesis, 50 cases of AFX were stained immunohistochemically for CD117 to determine the diagnostic value of this antibody. Cases were also stained for tryptase to identify mast cells, which are CD117 positive. In addition, S100 and CD1a stains were performed to assess any possible contribution of melanocytes or Langerhans cells to CD117 staining. Only 1 of 50 AFXs (2%) showed CD117 positivity in the neoplastic cells, but all tumors demonstrated included CD117- and tryptase-positive mast cells in similar distribution. CD117 is only rarely stainable in the neoplastic cells of AFX and is therefore not useful in identifying these tumors. Mast cells are also CD117 positive, frequently present in AFX, and can lead to misinterpretation. Using immunohistochemistry for mast cell tryptase may be of value where there is doubt as to the nature of CD117-positive cells in neoplasms.

An approach to malignant mammary phyllodes tumors detection

BACKGROUND/AIM

Mammary phyllodes tumors (MPT) are uncommon fibroepithelial (biphasic) neoplasms whose clinical behavior is difficult to predict on the basis of histological criteria only. They are divided into benign, borderline malignant and malignant groups. Sometimes it appears difficult to distinguish these tumors from other types of soft tissue sarcomas. Because of the relatively scant data on the role of biological markers in MPT histogenesis, we have decided to undertake the following study, trying to shed more light on the issue by investigating the following elements that make up MPT: their histological patterns, biological behavior, enzymohistochemical, histochemical and immunohistochemical characteristics (ICH) together with the mast cell analysis.

METHODS

We examined the biopsy material of 35 MPT in our laboratory. Enzymohistochemistry was performed on frozen sections (method of Crowford, Nachlas and Seligman). The used methods were classical hematoxylin-eosin (H & E); histochemical Massontrichrome, Alcian-blue, Periodic acid Schiff and immunohistochemical LSAB2 method (DacoCytomation). Ki-67, c-kit, vimentin, estrogen receptor (ER), progesterone receptor (PR) and Her-2 oncoprotein immunohistochemistry was performed on all tumors.

RESULTS

The patients were ranged per age from 30--62 years (mean 43.3 years, median 39 years). A total of 35 cases of MPT were included: 20 benign (57%), 6 borderline malignant (17%) and 9 malignant (26%). Twenty-two patients (62.8%) underwent segmental mastectomy, while 13 (37.2%) had total mastectomies. Twenty-eight patients had negative surgical margins at original resection. The mean size of malignant MPT (7.8 cm) was larger than that of benign MPT (4.5 cm). Significant features of the malignant MPT were: stromal cellularity, stromal cellular atypism, high mitotic activity, atypic mitoses, stromal overgrowth, infiltrative tumor contour and heterologous stromal elements. Benign MPT showed strong enzymohistochemical Leucine Amino Peptidase (LAP) activity in both epithelial and stromal components while it was weak or absent in the epithelial parts of the malignant tumors. Acid mucopolysacharides were present in the stromal component of all types of these tumors. Benign MPT had a lower Ki-67 than did borderline malignant MPT (4 versus 28). Malignant MPT had a greater than 8-fold higher Ki-67 activity than did benign tumors (35 versus 4). Intracyto-plasmatic c-kit expression was associated with a pathological diagnosis of malignant MPT, correlating with increasing grade (p < 0.05). In hypercellular stroma of borderline malignant and especially malignant forms of MPT, high activity of ER in mast cells was confirmed. Oncoprotein Her-2 activity, mostly in epithelial components, correlated with the degree of malignant progression of MPT (p < 0.05).

CONCLUSION

Besides the well-known malignant features additional parameters have been found to be high Ki-67 and c-kit stromal expressions, and weak LAP activity in the epithelial part of malignant MPT, as well as mast cells with a high expression of ER.

Mastocytosis of the female breast

A subset of patients with systemic mastocytosis may manifest with extracutaneous involvement. To the best of our knowledge, mastocytosis of the human breast has not been described. This study reports a case with mastocytosis involving the breasts of a 33-year-old woman associated with mammary hypertrophy (breast mastocytosis). The potential for infiltrating mast cells to mimic lobular carcinoma is emphasized and the relationship to breast hypertrophy in this case is discussed.