Smooth muscle cell differentiation in mammary stromo-epithelial lesions with evidence of a dual origin: stromal myofibroblasts and myoepithelial cells

Mammary stromal-epithelial lesions with myofibroblastic stroma and HMGA2 overexpression linked smooth muscle differentiation, a case series from single institution

Fibroadenoma and phyllodes tumor are the prototypical mammary fibroepithelial lesions (FELs). Recently, a subset of FELs, identified as stromal-epithelial lesion (SEL) with myofibroblastic stroma have been labelled as myofibroepithelial nodule (MFN). The MFN stromal cells are diffusely positive for SMA immunostaining and frequently show unusual histological features including irregular borders. There is limited literature on FELs with myofibroblastic or smooth muscle stroma. The etiology of the variation in the FEL stromal histology and its clinical significance is unknown. In this short report we describe clinicopathologic features of six FELs with myofibroblastic and/or smooth muscle stroma. We also report immunohistochemical overexpression of HMGA2 in 2 FELs that contained stromal smooth muscle differentiation suggesting a link to mammary myoid hamartoma. On limited follow up all the 6 FELs with myofibroblastic or smooth muscle stroma had benign outcome. The HMGA2 overexpressing FEL with smooth muscle stroma and myoid hamartoma of the breast show overlapping etiology, and histological features.

Benign myofibroblastic/epithelial lesions of the breast with minimally infiltrative margins

A minority of mixed fibro-epithelial lesions of the breast lacks both fibroadenoma and phyllodes architectural patterns and have been previously labeled with different terms, including "hamartomas", "myoid/muscular hamartomas", "benign fibroadenomatous lesions" or "stromo-epithelial lesions of the breast". This study emphasizes the clinico-pathologic features of 5 cases of mammary benign fibro(stromo)-epithelial lesions sharing as a common morphologic theme the presence of minimally infiltrative margins due to the overgrowth of the stromal component into the surrounding fibro-fatty tissue. Notably the radiological features were suspicious for malignancy in 3 out of 5 cases. The following histologic features were seen in all cases: i) an epithelial component of benign glandular structures exhibiting the morphological spectrum of fibro-cystic disease; ii) a stromal component of bland-looking spindle cell myofibroblasts (vimentin + and α-smooth muscle actin +) set in a variably fibro-myxoid stroma. The present paper contributes to widen the morphological spectrum of the benign fibro-epithelial lesions of the breast, emphasizing the possibility that some cases, exhibiting a predominant myofibroblastic stromal component and minimally infiltrative margins, may be confused with other primary spindle cell mimickers of the breast. Accordingly, we propose the descriptive term "benign myofibroblastic/epithelial lesions of the breast with minimally infiltrative margins" for these previously underrecognized lesions.

Invasive Micropapillary Carcinoma of the Breast: An Immunohistochemical Study of Neoplastic and Stromal Cells

A 59-year-old woman complained of a palpable mass in the right breast, and a needle biopsy disclosed small clusters of neoplastic cells in the fibrous stroma. The small clusters did not contain fibrovascular cores but exhibited micropapillary configuration. Epithelial membrane antigen (EMA) immunohistochemistry confirmed the reverse polarity of the neoplastic cells. Additionally, the plasma membrane of many neoplastic cells stained with E-cadherin and f-catenin. Myofibroblasts, which were positive for alpha smooth muscle actin (ASMA) and negative for cytokeratin 14, were abundant in the neoplastic stroma, but no CD34-positive stromal cells were observed in the neoplastic stroma. For comparison, 3 additional cases of invasive micropapillary carcinoma (IMC) and 4 cases of invasive ductal carcinoma (IDC) were studied. Similar results for stromal cells were obtained in all cases. Our results from this preliminary investigation suggest that CD34-positive stromal cells may disappear from the stroma of IMC as well as IDC.

Alterations of collagen-producing cells in human pituitary adenomas

Extracellular matrix (ECM) is essential in tissue physiology and pathologic conditions such as tumorigenesis. ECM affects tumor cell behavior, proliferation, and metastasis. Pituitary adenomas vary in their clinical characteristics, including ECM deposition. However, the mechanism of desmoplasia in pituitary adenoma is not well understood. The present study focused on the principal component of ECM, collagen, and attempted to characterize collagen-producing cells in pituitary adenomas. Specimens of human pituitary adenomas and control pituitary were obtained during surgery. In situ hybridization for collagen I and III and immunohistochemistry for α-smooth muscle actin (a pericyte marker) and cytokeratin (an epithelial cell marker) were performed. The results showed that pericytes were the sole collagen-producing cells in control pituitary, while four types of collagen-producing cells were present in pituitary adenomas: pericytes, myofibroblasts, fibroblasts, and newly characterized "myoepithelial-like cells". Azan staining showed that fibrous matrix deposition varied among pituitary adenomas and that the area of fibrosis was associated with the number and types of collagen-producing cells. These results suggest that changes in the number and type of collagen-producing cells influence ECM arrangement, which may in turn reflect pathologic characteristics in pituitary adenomas.

Squamous/epidermoid differentiation in normal breast and salivary gland tissues and their corresponding tumors originate from p63/K5/14-positive progenitor cells

A small group of tumors of breast and salivary glands contains squamous/epidermoid elements as a constitutive feature (e.g., squamous carcinoma, syringomatous tumors, and mucoepidermoid carcinoma). Other tumors (e.g., pleomorphic adenoma, adenomyoepithelial tumors, and adenoid cystic carcinoma) may show occasionally squamous differentiation. Furthermore, squamous metaplasia may be observed in non-neoplastic breast and salivary tissues. However, the histogenesis of these squamous differentiations is far from being understood. Based on our earlier in situ triple immunofluorescence and quantitative reverse transcription (RT)-PCR experiments for basal keratins K5/14 and p63 as well as for glandular keratins (K7/K8/18), squamous keratins (K10 and K13), and myoepithelial lineage markers (smooth muscle actin, SMA), we here traced the squamous/epidermoid differentiation lineage of 60 tumors of the breast and/or salivary glands, cultured tumor cells of 2 tumors, and of 7 squamous metaplasias of non-neoplastic breast and salivary tissues. Our results indicate that both the neoplastic lesions as well as the non-neoplastic squamous metaplasia contain p63/K5/14+ cells that differentiate toward K10/13+ squamous cells. Thus, cells with squamous/epidermoid differentiation undergo a transition from its original p63/K5/14+ precursor state to K10/13+ squamous lineage state, which can be pictured by triple-immunofluorescence experiments. Given the immunophenotypic similarity of p63/K5/14+ tumor cells to their physiological p63/K5/14+ counterparts in normal breast and salivary duct epithelium, we suggest that these cells provide an important histogenetic key to understanding the pathogenesis of squamous differentiation both in normal breast/salivary gland tissues and their corresponding tumors.

Evaluation of eligibility criteria in living donor liver transplantation for hepatocellular carcinoma by α-SMA-positive cancer-associated fibroblasts

The eligibility criteria of liver transplantation (LT) for hepatocellular carcinoma (HCC) must clearly confirm the prognosis not only from pathological diagnosis but also from pre-operative imaging diagnosis. In the present study, we evaluated published eligibility criteria for LT based on both pre-operative imaging diagnosis and pathological diagnosis using living donor liver transplantation (LDLT) recipients at our hospital by α-smooth muscle actin (SMA)-positive cancer-associated fibroblasts (CAFs) in HCC. The Up-to-seven (Up-to-7), Asan and Tokyo criteria were evaluated, in both overall survival and HCC disease-free survival, to be statistically significantly beneficial criteria to define post-LDLT prognosis. Recipients only within Up-to-7 criteria based on both pre-operative imaging diagnosis and pathological diagnosis survived without HCC recurrence. Recipients with proliferation of α-SMA-positive CAFs in HCC had significantly poorer prognosis. All survival recipients without HCC recurrence, who were above the Up-to-7 criteria in pathological diagnosis, had no proliferation of α-SMA-positive CAFs. As a result of multivariate analysis, the significant independent factors defining prognosis of recipients after LDLT for HCC were Up-to-7 criteria and proliferation of α-SMA-positive CAFs. The ideal eligibility criteria for LDLT with HCC is Up-to-7 criteria and α-SMA-positive CAFs was considered to be an important factor in HCC recurrence. LDLT should be limited to recipients within Up-to-7 criteria or without proliferation of α-SMA-positive CAFs.

K5/K14-positive cells contribute to salivary gland-like breast tumors with myoepithelial differentiation

Salivary gland-like tumors of the breast show a great variety of architectural patterns and cellular differentiations such as glandular, myoepithelial, squamous, and even mesenchymal phenotypes. However, currently little is known about the evolution and cellular differentiation of these tumors. For that reason, we performed an in situ triple immunofluorescence lineage/differentiation tracing (isTILT) and qRT-PCR study of basal (K5/K14), glandular (K7/K8/18), and epidermal-specific squamous (K10) keratins, p63, and smooth muscle actin (SMA; myoepithelial marker) with the aim to construct and trace different cell lineages and define their cellular hierarchy in tumors with myoepithelial differentiation. isTILT analysis of a series of 28 breast, salivary, and lacrimal gland tumors, including pleomorphic adenomas (n=8), epithelial-myoepithelial tumors (n=9), and adenoid cystic carcinomas (n=11) revealed that all tumor types contained K5/K14-positive progenitor cells in varying frequencies from a few percent up to 15%. These K5/K14-positive tumor cells were found to differentiate to glandular- (K8/18-positive) and myoepithelial-lineage (SMA-positive)-specific cells and were also shown to generate various heterologeous cell differentiations such as squamous and mesenchymal progenies. p63 was co-expressed with K5/K14 in basal-like progenitor cells, myoepithelial, and squamous cells but not in glandular cells. Our results show that the corresponding counterpart tumors of breast and salivary/lacrimal glands have identical cellular compositions. Taken together, our isTILT and RNA-expression data indicate that look-alike tumors of the breast represent a special subgroup of basal-type tumors with benign or usually low malignant potential.

Instigation of Notch signaling in the pathogenesis of Kaposi's sarcoma-associated herpesvirus and other human tumor viruses

The Notch pathway is a highly conserved signaling circuit with a critical role in cell-fate determination and tumor initiation. Notch is reported to regulate various key events in tumor progression, such as angiogenesis, maintenance of cancer stem cells, resistance to therapeutic agents and metastasis. This review describes the intimate interplay of human tumor viruses with the Notch signaling pathway. Special attention is paid to Kaposi's sarcoma-associated herpesvirus, the etiological agent of Kaposi's sarcoma and rare lymphoproliferative disorders. The past decade of active research has led to significant advances in understanding how Kaposi's sarcoma-associated herpesvirus exploits the Notch pathway to regulate its replication phase and to modulate the host cellular microenvironment to make it more favorable for viral persistence and spreading.

Combined Epithelial-Myoepithelial Lesions of the Breast

Epithelial-myoepithelial proliferations of the breast are a heterogeneous poorly defined group of lesions characterized morphologically by dual differentiation into ductal (luminal) and myoepithelial cells. They include neoplastic and non-neoplastic entities that have overlapping morphologic features that may give rise to diagnostic difficulty. Many of these entities are low grade or of uncertain malignant potential but the biology of some of these rare lesions remains to be elucidated. This article discusses the differential diagnosis of epithelial-myoepithelial lesions of the breast and highlights the morphologic features of some of these entities.

Origin and differentiation of breast nipple syringoma

Similarities in morphology and in glandular and squamous differentiation patterns amongst syringomas of the breast nipple and of the skin suggest a common nature, but the origin of nipple syringoma remains undefined. Using triple immunofluorescence analysis, we found that cells immunopositive for basal keratins K5 and 14 undergo differentiation into glandular and squamous cell lineages. Both tumour types expressed K10, indicative of squamous lineage, but there were specific differences in their glandular lineage. In contrast to the breast nipple syringoma, which expressed glandular keratins K8/18/19, syringoma of the skin only expressed the glandular keratin K19. Therefore, syringomas of the breast nipple and of the skin resemble glandular lineages of the breast nipple duct or eccrine duct epithelium, respectively. From these results we conclude that K5/14-positive cells of the breast nipple ducts are the putative cells of origin for syringomas of the nipple, which highlights the organotypic glandular differentiation potential.

Tumor-secreted lysophostatidic acid accelerates hepatocellular carcinoma progression by promoting differentiation of peritumoral fibroblasts in myofibroblasts

Hepatocellular carcinoma (HCC) occurs in fibrotic liver as a consequence of underlying cirrhosis. The goal of this study was to investigate how the interaction between HCC cells and stromal fibroblasts affects tumor progression. We isolated and characterized carcinoma-associated fibroblasts (CAFs) and paired peritumoral tissue fibroblasts (PTFs) from 10 different patients with HCC and performed coculture experiments. We demonstrated a paracrine mechanism whereby HCC cells secrete lysophostatidic acid (LPA), which promotes transdifferentiation of PTFs to a CAF-like myofibroblastic phenotype. This effect is mediated by up-regulation of specific genes related to a myo/contractile phenotype. After transdifferentiation, PTFs expressed α-smooth muscle actin (α-SMA) and enhanced proliferation, migration, and invasion of HCC cells occur. A pan-LPA inhibitor (α-bromomethylene phosphonate [BrP]-LPA), or autotaxin gene silencing, inhibited this PTF transdifferentiation and the consequent enhanced proliferation, migration, and invasion of HCC cells. In vivo, PTFs coinjected with HCC cells underwent transdifferentiation and promoted tumor progression. Treatment with BrP-LPA blocked transdifferentiation of PTFs, down-regulated myofibroblast-related genes, and slowed HCC growth and progression. Patients with larger and metastatic HCC and shorter survival displayed higher serum levels of LPA. Analysis of microdissected tissues indicated that stroma is the main target of the LPA paracrine loop in HCC. As a consequence, α-SMA-positive cells were more widespread in tumoral compared with paired peritumoral stroma.

CONCLUSION

Our data indicate that LPA accelerates HCC progression by recruiting PTFs and promoting their transdifferentiation into myofibroblasts. Inhibition of LPA could prove effective in blocking transdifferentiation of myofibroblasts and tumor progression.

A rare case of recurrent myoid hamartoma mimicking malignancy: imaging appearances

Myoid hamartoma is an uncommon type of breast hamartoma and its recurrence is very rare. We report the imaging appearance of an unusual case of recurrent myoid hamartoma of the breast mimicking malignancy in a 43-year-old woman. Although the mammographic and ultrasonographic findings have long been described in the literature, MR finding with a dynamic study has not, to the best of our knowledge, been reported previously.

Myoid (Muscular) Hamartoma of the Breast: Case Report and Review of the Literature

BACKGROUND: Myoid (muscular) hamartoma (MH) of the breast is a rare benign tumour-forming lesion composed of differentiated mammary glandular and stromal structures, fatty tissue, and areas of smooth muscle. It is considered to be a variant of mammary hamartoma. CASE REPORT: We report the case of a 46-year-old woman with MH, and provide a literature review explaining the origin of smooth muscle cells. Histologically, the tumour consisted of fibrolipomatous stroma containing ductal and lobular structures of the mammary gland located mainly at the tumour borders. The glandular structures showed signs of micro- and macrocystic changes, apocrine metaplasia, and adenosis. The dominant feature was the presence of a fascicular formation of spindle cells, predominantly in central parts, with incursion between glandular structures. Immunohistochemically, foci of smooth muscle tissue were positive for desmin, smooth muscle actin, and h-caldesmon. Oestrogen and progesterone receptors (PR) showed positive expression which was markedly higher for PR. There was negative expression of CD34, S-100 protein, and CD10. CONCLUSIONS: The origin of smooth muscle cells in MH is unknown. However, it is presumed to be derived from hormonally responsive breast stromal cells by smooth muscle metaplasia, based on evidence of hormone receptor expression in the lesion.

Myofibroblastoma arising in mammary hamartoma: a case report

Myofibroblastoma (MFB) is a rare mesenchymal tumor arising in breast's soft tissue with a great variety of microscopic features that can be mistaken with a wide variety of biphasic lesions. The authors report a rare case of myofibroblastoma of the breast arising in a mammary hamartoma (MH), present a review of the clinicopathological features of these lesions, and make some diagnostic considerations. The tumour consisted of a well-circumscribed nodule. MFB component comprised about fifty percent of the lesion and was made up of bipolar spindle cells arranged in fascicular clusters separated by bands of hyalinized collagen. There were fat cells and several residual hamartoma glands intermingled and distorted in MFB area. MFB component was positive for Desmin, CD34, bcl-2, and Calponin. To the best of our knowledge, MFB has not been reported in MH, neither has any of the reports described mammary glands joined within MFB.

Cancer associated fibroblasts (CAFs) in tumor microenvironment

Cancer associated fibroblasts (CAFs) is one of the most crucial components of the tumor microenvironment which promotes the growth and invasion of cancer cells by various mechanisms. CAFs demonstrate a high degree of heterogeneity due to their various origins; however, many distinct morphological features and physiological functions of CAFs have been identified. It is becoming clear that the crosstalk between the cancer cells and the CAFs plays a key role in the progression of cancer, and understanding this mutual relationship would eventually enable us to treat cancer patients by targeting CAFs. In this review, we will discuss the latest findings on the role of CAFs in tumorigenesis and metastasis as well as potential therapeutic implication of CAFs.

Stromal myofibroblasts are drivers of invasive cancer growth

Tissue integrity is maintained by the stroma in physiology. In cancer, however, tissue invasion is driven by the stroma. Myofibroblasts and cancer-associated fibroblasts are important components of the tumor stroma. The origin of myofibroblasts remains controversial, although fibroblasts and bone marrow-derived precursors are considered to be the main progenitor cells. Myofibroblast reactions also occur in fibrosis. Therefore, we wonder whether nontumorous myofibroblasts have different characteristics and different origins as compared to tumor-associated myofibroblasts. The mutual interaction between cancer cells and myofibroblasts is dependent on multiple invasive growth-promoting factors, through direct cell-cell contacts and paracrine signals. Since fibrosis is a major side effect of radiotherapy, we address the question how the main methods of cancer management, including chemotherapy, hormonotherapy and surgery affect myofibroblasts and by inference the surrogate endpoints invasion and metastasis.

Myoid hamartoma of the breast: a case report and review of the literature

Myoid hamartomas of the breast are extremely rare breast lesions, with a poorly understood pathogenesis. A 60-year-old woman presented with a palpable mass in the right breast. Breast ultrasonography and mammography showed the presence of a breast lesion with benign characters, but were not diagnostic. A local excision of the mass was performed; histology revealed that the tumor was composed of epithelial and stromal cells. Histological and immunohistochemical findings established the diagnosis of myoid hamartoma. The patient is well 4 years later without tumor recurrence. Breast myoid hamartomas are exceptionally rare benign lesions; complete surgical excision achieves cure.

Myoid hamartoma of the breast: case report and review of the literature

Hamartoma is a mass of disorganized but mature specialized cells or tissue indigenous to the particular site. They can occur anywhere in the body, and their common sites of occurrence include lungs, skin, hypothalamus, spleen, and kidneys, of which lungs are the most common. We report a rather unusual, largely unrecognized case of myoid hamartoma of the breast. They constitute approximately 3.9%-4.8% of breast tumors. Myoid hamartomas belong to a spectrum of benign breast lesion of dual origin, containing myoepithelial and myofibroblastic components in varying proportions. They are usually asymptomatic but can present as well-circumscribed masses that do not possess specific diagnostic histologic features, and diagnosis is, therefore, difficult. In contrast to many other benign or malignant breast lesions, the diagnosis of hamartoma can easily be missed. Herein, we discuss the importance of radiologic, immunohistochemical studies and histopathologic findings in the diagnosis of a myoid hamartoma. Extensive review of the literature has been done for this purpose, and we highlight the clinical presentation and therapeutic aspects of this breast lesion.

Estrogen receptor-beta is expressed in stromal cells of fibroadenoma and phyllodes tumors of the breast

An estrogen dependency has been suggested for the growth of fibroadenomas: however, thus far, none of the steroid hormone receptors acting on breast tissues has been demonstrated in the stroma of breast fibroepithelial lesions. In this study, the expression of estrogen receptor (ER)-alpha and -beta was investigated by immunohistochemistry in 33 fibroadenomas and in 30 benign, three borderline and seven malignant phyllodes tumors, all with spindle cell growth and in one distant metastasis. In addition, the presence of ER-beta mRNA and its variants was evaluated by RT-PCR in microdissected stroma. The possible correlation between hormone receptor expression and differentiation processes of stromal cells was investigated by smooth muscle actin and calponin immunostaining. ER-beta was the only hormone receptor expressed by stroma of fibroadenomas and phyllodes tumors, both at protein and mRNA level. The highest percentage of ER-beta was observed in fibroadenomas with cellular stroma and in phyllodes tumors. In both lesions, ER-beta-positive stromal cells showed expression of smooth muscle actin and/or calponin, as demonstrated by double immunostaining. In addition, the mean age at diagnosis was significantly lower in patients with ER-beta-positive vs ER-beta-negative fibroadenomas. In contrast, in phyllodes tumors, ER-beta expression was higher in older patients. In conclusion, (i) only ER-beta is detected in the stroma of fibroadenomas and phyllodes tumors; (ii) its expression correlates with the expression of smooth muscle markers and suggests a role of ER-beta in myofibroblastic differentiation of stromal cells. These two results, together with the young age of patients carrying fibroadenomas with highly ER-beta-positive stroma cells, may further indicate a hormone-receptor mechanism involved in regulating the growth of fibroadenomas. Conversely, the older age of patients with ER-beta-rich phyllodes tumors suggests that mechanisms, probably independent from estrogen stimulation, act on the growth of these tumors.

Comparative study of cellular and extracellular matrix composition of native and tissue engineered heart valves

Tissue engineering of heart valves utilizes biodegradable or metabolizable scaffolds for remodeling by seeded autologous cells. The aim of this study was to determine and compare extracellular matrix (ECM) formations, cellular phenotypes and cell location of native and tissue engineered (TE) valve leaflets. Ovine carotid arteries, ovine and porcine hearts were obtained from slaughterhouses. Cells were isolated from carotid arteries and dissected ovine, porcine and TE leaflets. TE constructs were fabricated from decellularized porcine pulmonary valves, seeded ovine arterial cells and subsequent 16 days dynamic in vitro culture using a pulsatile bioreactor. Native and TE valves were studied by histology (hematoxylin-eosin, resorcin-fuchsin, Movat pentachrome), NIR femtosecond multiphoton laser scanning microscopy and scanning electron microscopy (SEM). Cells of native and TE tissues were identified and localized by immunohistochemistry. Arterial, valvular and re-isolated TE-construct cells were processed for immunocytochemistry and Western blotting. ECM analysis and SEM revealed characteristical and comparable structures in native and TE leaflets. Most cells in native leaflets stained strongly positive for vimentin. Cells positive to alpha-smooth muscle actin (alpha-SMA), myosin and calponin were only found at the ventricular (inflow) side of ovine aortic and porcine pulmonary valve leaflets. Cells from TE constructs had a strong expression of vimentin, alpha-SMA, myosin, calponin and h-caldesmon throughout the entire leaflet. Comparable ECM formation and endothelial cell lining of native and TE leaflets could be demonstrated. However, immunostaining revealed significant differences between valvular cell phenotypes of native and TE leaflets. These results may be essential for further cardiovascular tissue engineering efforts.

Sparse and wavy hair: a new model for hypoplasia of hair follicle and mammary glands on rat chromosome 17

Mutant animals in the skin and hair have been used to identify important genes in biomedical research. We describe a new mutant rat, sparse and wavy hair (swh), that spontaneously arose in a colony of inbred WTC rats. The mutant phenotype was characterized by sparse and wavy hair, which was most prominent at age 3-4 weeks, and was inherited in an autosomal recessive manner. The swh/swh rats showed impaired gain of body weight, and their hair follicles were reduced both in number and size, associated with hypoplasia of the sebaceous glands and the subcutaneous fat tissue. Female swh/swh rats were unable to suckle their offspring. Their mammary glands were hypoplastic, and differentiation of mammary epithelial and myoepithelial cells was impaired. Linkage analysis of 579 backcross rats localized the swh locus to a .35-cM region between D17Rat131 and D17Rat50 in the distal end of rat Chr 17. The swh locus spanned the 3.7-Mb genomic region where 24 genes have been mapped and corresponded to the centromere region of the mouse Chr 2 or the region of the human Chr 10p11.1-p14. None of the genes or loci described in mouse or human hair and skin diseases mapped to these regions. These findings suggest that the rat swh is a novel mutation associated with impaired development of the skin appendages, such as hair follicles, sebaceous glands, and mammary glands, and will provide an experimental model to clarify a gene and mechanisms for development of skin appendages.