The myoepithelium in cystic hyperplastic mastopathy

Application of immunostaining for muscle specific actin in detection of myoepithelial cells in breast fine-needle aspirates

Myoepithelial cells play an important role in the interpretation of breast fine-needle aspiration biopsy, since these cells are believed to be a component of a benign process in breast lesions. Myoepithelial cells are usually easy to recognize, however, other cells can morphologically simulate myoepithelial cells and make the distinction difficult. To assess the feasibility of immunostaining as an adjunct to identify myoepithelial cells, we have used immunocytochemistry using monoclonal antibody against muscle specific actin (MSA) in our breast fine-needle aspirates. Herein, we report our experience in immunocytochemical detection of myoepithelial cells using labeled Streptavidin Biotin Detection System on destained Papanicolaou stained smears and cell block preparations obtained from breast aspirates.

Histopathology of myoepithelial (basocellular) hyperplasias in adenosis and epitheliosis of the breast demonstrated by the reactivity of cytokeratins and S100 protein. An analysis of heterogenic cell proliferations in 90 cases of benign and malignant breast diseases

This study on the different types of epithelial hyperplasia in fibrocystic disease was inspired by the observation of myoepithelial (basocellular) hyperplasia identified by strong expression of S100 protein and a weak reaction with antibodies against cytokeratin (KL1) in cells forming solid and acinar buds. The cells do not contain immunohistochemically detectable actin or desmin. Glandular transformation and proliferation give rise to basocellular circumductal adenosis. Normal breast tissue, 51 cases of fibrocystic disease with mild, florid and atypical hyperplasias, 7 fibroadenomas and 20 cases of carcinoma in situ were studied and a semiquantitative analysis revealed basal buds and adenosis in less than 40% of cases of mild hyperplasia and up to 73% in florid hyperplasia. Epitheliosis is characterized by a heterogeneous cell pattern with cells positive for S100 protein in 30-60%, but in small ducts up to 100% with an immediate connection to the basal cell layer were positive. Carcinoma in situ contained very rare tumour cells positive for S100 protein. The cells expressing S100 protein in terminal ducts, in adenosis and epitheliosis showed only some of the characteristics of myoepithelial cells, since they lack immunoreactivity with antibodies against actin. These basal clear cells are interpreted as transitional or indeterminate cells with features of myoepithelial precursor cells, but with the ability to develop basocellular nodular and glandular hyperplasia in the ductulo-lobular units in cases of adenosis and juvenile fibroadenoma.

Immunohistochemical localization of myoepithelial cells and basement membrane in normal, benign and malignant human breast lesions

Distributions of actin and type IV collagen were investigated immunohistochemically as markers for myoepithelial cells and basement membranes. Carnoy's and Methacarn-fixed, paraffin-embedded tissues from 103 human breast lesions from 103 patients were examined; 65 with carcinomas, 27 with mastopathies, 9 with fibroadenomas and 2 with phyllodes tumours. Fifty-five samples of the normal mammary gland tissue adjacent to tumours were also included for comparison. In normal breast and benign breast diseases, type IV collagen was identified around the mammary glandular cells and actin-positive cells were demonstrated to attach to basement membranes. In noninvasive carcinomas, type IV collagen was found as a continuous lining around a cell nest, while actin-positive cells were usually absent in ductal but quite numerous in lobular carcinomas. In invasive carcinomas, type IV collagen was fragmented or absent and actin-positive cells were very uncommon around the fragmentary basement membranes. These results suggest that the different distributions of myoepithelial cells and basement membrane material is useful in the differential diagnosis of surgical pathology of the breast.

The myoepithelial cell: embryology, function, and proliferative aspects

Myoepithelial cells form an integral part of the secretory and ductular portion of most glands. They share a common origin with lumenal epithelial cells and influence proliferation and differentiation of developing terminal glandular buds by producing a scaffold of basement membrane proteins. Their contractile capacity, controlled by hormonal and neural mechanisms, plays an important role in propulsion of secretions. Furthermore, myoepithelial cells maintain glandular structural integrity and transport metabolites to secretory cells. The advent of modern immunochemistry made identification of specific myoepithelial cell markers possible which facilitated studies on their presence and behavior in disease processes. Although the significance of many myoepithelial alterations is speculative, some have proved valuable in determining the histogenesis of glandular lesions.

The galactocoele: a light- and electronmicroscopic study

The histological and ultrastructural appearances of a galactocoele are illustrated and compared with previous descriptions. For the first time, microscopic evidence is presented to show that a galactocoele arises from dilated ducts filled with milk produced in the surrounding breast.

Basement membrane confinement of epithelial tumor islands in benign and malignant ameloblastomas

The extent of basement membrane confinement among 5 cases of ameloblastoma and a malignant counterpart were studied by immunohistochemistry. For these studies, antibodies to 2 basement membrane components, Type IV collagen and laminin, were studied by immunohistochemistry. Our results show that the tumor islands of ameloblastomas are circumferentially delineated by a linear staining to both antibasement membrane antibodies, and that these findings were consistent for all of the patterns of ameloblastoma investigated. These data suggest that ameloblastomas spread into tissue spaces by expanding their compartmental volumes rather than by secreting proteinases that disrupt their basement membranes compartmental barriers. In contrast, the single case of malignant ameloblastoma investigated was not delineated by circumferential linear basement membrane components. However, this tumor and all of its metastases did contain numerous focal areas of Type IV collagen and laminin immunoreactive materials. Collectively, these studies indicate that the use of specific antibodies to basement membrane components may help to differentiate ameloblastomas from malignant lesions.

Immunohistochemical studies on myoepithelial changes in breast tumors

Specific rabbit antisera directed against human uterine myosin were prepared and used for immunohistochemical studies on myoepithelial cells (MECs) in some breast tumors. In fibroadenomas, MECs were observed confined to the periductal portions but not in the stroma. In infiltrating duct carcinomas, MECs were also present as a distinctive periductal layer. Moreover, they were also seen in the infiltrating area, either associated with a small nest of carcinoma cells or freely in the stroma. Larger nests of medullary carcinomas usually were not accompanied by any layer of MECs. No MECs were detected in lobular carcinomas as far as the infiltrating area was concerned. It is suggested from these results that the behavior of MECs is significantly different, depending upon the types of breast tumors. It also appears that the present method may be useful for further analysis of the origin and growth pattern in various breast tumors.

Nonspecific alkaline phosphatase activity in normal and diseased human breast

Nonspecific alkaline phosphatase activity was identified in human normal and diseased breasts with the use of the calcium-cobalt, the lead-nitrate, and the azo-dye methods. The results varied not only with the staining method, but also with the functional status of the breast structures. In normal, dysplastic, and fibroadenomatous tissues there was a strong parallelism between myoepithelial and capillary enzyme activities. The calcium-cobalt method was the only technique which allowed staining of carcinoma cells; cancer stromal enzyme activity was evidenced only with the use of the same method. Our findings suggest that nonspecific alkaline phosphatase activity probably reflects a functional status of the labelled structures; the enzyme activity of myoepithelial cells is variable and not really specific.

ATPase activity in the breast: a comparison between three methods

Adenosine triphosphatase enzymatic activity was investigated in human approximatively normal, dysplastic and neoplastic mammary tissue, by three different methods. Staining intensity varied within wide limits; myoepithelial cells and blood vessels showed similar enzymatic activity. Epithelial cells reacted only faintly, or not at all; carcinoma cells were never labelled. Stromal response was highly variable. The calcium-cobalt method of Padykula and Herman gave more intense reactions than the lead-nitrate procedure of Wachstein and Meisel, either in the original form or according to the modifications recommended by Russo and Wells. With the latter method the sharpness of stain deposits on the different structures was markedly enhanced. The functional significance of ATPase activity is discussed.

Immunohistochemical identification of actomyosin-containing (myoepithelial) cells in non-neoplastic and neoplastic tissues

Actomyosin-containing cells in both non-neoplastic and neoplastic tissues of the salivary gland, lung, breast and some other organs were studied by immunofluorescent microscopy using antiactomyosin rabbit serum. In the breast, myoepithelial-like cells with positive immunofluorescence in the cytoplasm were observed not only in sclerosing adenosis and fibroadenoma but also in scirrhous and medullary-tubular duct carcinomas. No positive cells were observed in medullary carcinomas with lymphoid infiltration. The actomyosin positive cells were also seen at the outer layer of tubules of "mixed tumors" and of cell nests in adenoid cystic carcinoma and in myoepithelioma of the salivary gland, but not in the metaplastic squamous cells or in the cells of myxomatous and chondroid areas of "mixed tumor". In carcinoma of the lung, actomyosin-positive cells were observed in adenoid cystic carcinomas and adenocarcinoma of the bronchial gland type, but they were not seen in squamous cell carcinomas or papillary adenocarcinomas. It was concluded that the actomysoin-containing cells with structural appearances of myoepithelial cells in a variety of tumors were neoplastic myoepithelial cells.

Distribution of adenosine triphosphatase in infiltrating ductal carcinoma and non-neoplastic breast

The histochemical reaction for adenosine triphosphatase (ATPase) has previously been used to differentiate myoepithelial from epithelial cells in the breast and to investigate the possible contribution of myoepithelial cells to mammary carcinoma. Discrepancies in published reports prompted this study of ATPase in non-neoplastic breast and infiltrating ductal carcinoma. ATPase was localized mainly on myoepithelial cells of normal breast and was identified with significant frequency on epithelial cells in hyperplastic ducts. Infiltrating ductal carcinomas usually displayed a variable reactivity. In one instance, malignant cells demonstrating mucin production were found to be ATPase-positive. An infiltrating ductal carcinoma of the papillary type with apocrine features was also strongly ATPase-reactive. It is concluded that ATPase is not an exclusive marker of myoepithelial cells and, therefore, data resulting from the use of this enzyme to study the role of the myoepithelium in mammary carcinoma must be interpreted with caution.

Apocrine metaplasia in cystic hyperplastic mastopathy. Histochemical and ultrastructural observations

A histochemical and ultrastructural investigation of apocrine cells in the human breast has been carried out. These cells showed strong oxidative enzymatic activity, large numbers of mitochondria and numerous infoldings of the basal plasma membrane. In these features, such cells resemble the normal apocrine gland cells. These observations support the view that this lesion is a metaplastic change in normal breast epithelium.