Salivary Gland Tumors
Dongyou Liu in Tumors and Cancers, 2017
Possibly arising from progenitor cells residing within the ductal tributaries of the salivary glands, salivary gland tumors can be divided into luminal (acinar and ductal cells) and abluminal (myoepithelial and basal cells) types [2]. Myoepithelial cells are stellate shaped with cytoplasmic processes embracing the acini, or spindle shaped surrounding the intercalated ducts. As a dual epithelial and smooth muscle phenotype, myoepithelial cells produce an extracellular matrix such as basement membrane materials and myxoid substances leading to diverse histology of salivary gland tumors. Basal cells of the striated ducts, excretory ducts, and salivary ducts differ ultrastructurally from myoepithelial cells in the absence of myofilaments. Salivary gland tumors containing predominantly myoepithelial cells are considered biologically low grade, while those devoid of myoepithelium are considered high grade.
Actin and Myosin
Masahiko Mori in Histochemistry of the Salivary Glands, 2019
In normal and abnormal salivary glands, myosin and actin were mainly demonstrable in myoepithelial cells and ductal segments. Myoepithelial cells are evident surrounding acinar cells and between basal lamina of exocrine glands (salivary, lacrimal, and mammary). Their biologic features differ from smooth muscle cells in that they exhibit epithelial features. Scanning electronmicroscopic studies of myoepithelial cells in submandibular glands reveal stellate shapes with many processes, but those in parotid glands lack the terminal portion.9 Electronmicroscopic features of myoepithelial cells in salivary glands have been described in detail.10–12 The histogenesis of myoepithelial cells has been reported.13–15 Tumor cells in salivary gland tumors also stained variably.22–25 These contractile proteins may contribute to contraction, and participate in the integration and regulation of cytoplasmic organelles in cells.26–28
The Application of Thaw-Mount Autoradiography for the Localization of Putative Estrogen Target Cells in Human Mammary Lesions *
P. Pertschuk Louis, Lee Sin Hang in Localization of Putative Steroid Receptors, 2018
Breast biopsies of 17 cases of benign mammary lesions were studied.12 In four of nine fibroadenomas there was evidence of specific binding in ducts randomly scattered throughout the section and adjacent to other positive or negative ducts (Figure 3). On closer examination the specific labeling was seen to be confined to the nuclear region of epithelial cells, while histologically identifiable myoepithelial cells were negative. In positive ducts labeled epithelial cells were admixed with negative cells. Stromal cells were generally unlabeled. In the negative cases, there were no areas where specific uptake could be identified, and sections of tissue incubated only in 3H-estradiol resembled those incubated with excess unlabeled estradiol or DES. The few randomly scattered grains revealed no evidence of a predominantly nuclear localization. In fibrocystic disease, specific uptake was identified in three of eight cases and the distribution of the specific labeling resembled that seen in fibroadenomas.
Myoepithelioma of bone: ultrastructural, immunohistochemical and molecular study of three cases
Published in Ultrastructural Pathology, 2019
Paweł Kurzawa, Martin K. Selig, Patryk Kraiński, Michał Dopierała, G. Petur Nielsen
In summary: primary intraosseous myoepithelial tumors are rare neoplasms with only a handful of cases (approximately 30 according to Yun et al.41) described in the medical literature and therefore they may cause considerable diagnostic difficulties. In general, myoepithelioma cells express both epithelial markers (e.g. keratins, EMA) along with myoepithelial markers (e.g. muscle-specific actin).2,10–12 Molecularly, EWSR1 rearrangement may be seen in up to 45% soft tissue myoepitheliomas, mixed tumors of the skin and intraosseous myoepithelial tumors.2,19–24 However, absence of these immunohistochemical markers or EWSR1 rearrangement does not exclude a diagnosis of myoepithelial tumors. Hence, the ultrastructural examination may aid in the diagnosis of myoepithelial tumors. Ultrastructurally, myoepithelial cells are characterized by the presence of both tonofilaments (which suggest epithelial differentiation) and myofilaments (which suggest muscular differentiation) and can be further distinguished from smooth muscle cells by the presence of cytoplasmic processes.34,42 In our opinion, proper diagnosis of myoepithelioma of the bone rests on correlation of clinical, radiological, histochemical, immunohistochemical, molecular and ultrastructural features.
Physiology of sweat gland function: The roles of sweating and sweat composition in human health
Published in Temperature, 2019
The anatomical structure of the eccrine sweat gland, illustrated in Figure 2, consists of a secretory coil and duct made up of a simple tubular epithelium. The secretory tubule is continuous with and tightly coiled with the proximal duct. The distal segment of the duct is relatively straight and connects with the acrosyringium in the epidermis [5]. The secretory coil has three types of cells: clear, dark, and myoepithelial. As shown in Figure 2(c), clear cells are responsible for the secretion of primary sweat, which is nearly isotonic with blood plasma [6–8]. The clear cells contain a system of intercellular canaliculi, glycogen, and a large amount of mitochondria and Na-K-ATPase activity [5]. The dark cells are distinguishable by the abundance of dark cell granules in the cytoplasm. Their function is poorly understood, but thought to potentially act as a repository for various bioactive materials involved in regulation of clear cell and duct cell function [9,10]. The function of the myoepithelial cells is provision of structural support for the gland against the hydrostatic pressure generated during sweat production [5]. The duct has two cell layers: basal and luminal cells. Its primary function is reabsorption of Na and Cl ions as sweat flows through the duct, as shown in Figure 2(d). Most of the NaCl reabsorption occurs in the proximal duct, as these cells contain more mitochondria and Na-K-ATPase activity than that of the distal segment of the eccrine duct [5]. The result is a hypotonic final sweat excreted onto the skin surface [6,9].
Salivary myoepithelial cells: an addendum
Published in Ultrastructural Pathology, 2018
Asterios Triantafyllou, Lauge Hjorth Mikkelsen, Douglas R. Gnepp, Simon Andreasen, Jennifer L. Hunt, Kenneth O. Devaney, Vincent Vander Poorten, Alessandra Rinaldo, Stefan M. Willems, Alfio Ferlito
In addition to accumulation of lipofuscin, other ultrastructural alterations affect salivary myoepithelium following ductal ligation. In cats, while salivary parenchymal cells are variously lost after ligation, the myoepithelium persists. The persisting myoepithelial cells consequently become more prominent than normal, appear denser (Figure 6) and assume bizarre shapes. They show cytoplasmic processes protruding interstitially and associated with a thickened, likely redundant basement membrane (Figure 3, 5).1,18,47,48 Somewhat similar yet less extensive changes are seen in experimentally denervated, feline salivary glands and in chronic submandibular sialadenitis.1,18,19 The increased prominence of persistent myoepithelial cells in ligated glands is also visualized by enzyme histochemistry for alkaline phosphatase in the submandibular gland of cat,5049 and by immunohistochemistry for calponin in the parotid of rat.50 The immunohistochemical study interpreted the prominent calponin staining as a real increase attributable to proliferation or hyperplasia of the myoepithelial cells,50 although proliferation markers were not applied in that study.