Clear cell sarcoma of soft tissue with eccrine differentiation: A case report and review of the literature.

Clear cell sarcoma of soft tissue (CCSST) is a deep soft tissue tumor presenting in the extremities of young adults. Histopathologically, nests and sheets of polygonal cells with clear to eosinophilic cytoplasm separated by fibrous septa as well as occasional "wreath-like" giant cells are visualized. However, CCSST has been noted to have atypical histopathological features, such as epidermotropism or myxoid differentiation, or occurrence at unusual sites. Here, we present a case of eccrine ductal differentiation in CCSST. The patient, a 21-year-old woman, presented with a lump of 10-year duration sized 3 × 5 cm on the plantar surface of the fourth and fifth interdigital spaces. There had been an increase in size as well as pain and redness over 6 years. Besides the characteristic findings, there were ductal structures in continuity with the upper dermis indicative of ductal differentiation. The tumor stained positively for S100, HMB45, and succinic dehydrogenase; ducts stained positively for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA). CCSST was confirmed with cytogenetic analysis showing the translocation associated with EWSR1-ATF1 fusion gene. Therefore, ductal differentiation is a unique finding that should be considered when evaluating for CCSST.

Endothelial cell regulation of salivary gland epithelial patterning.

Perfusion-independent regulation of epithelial pattern formation by the vasculature during organ development and regeneration is of considerable interest for application in restoring organ function. During murine submandibular salivary gland development, the vasculature co-develops with the epithelium during branching morphogenesis; however, it is not known whether the vasculature has instructive effects on the epithelium. Using pharmacological inhibitors and siRNA knockdown in embryonic organ explants, we determined that VEGFR2-dependent signaling is required for salivary gland epithelial patterning. To test directly for a requirement for endothelial cells in instructive epithelial patterning, we developed a novel ex vivo cell fractionation/reconstitution assay. Immuno-depletion of CD31+ endothelial cells in this assay confirmed a requirement for endothelial cells in epithelial patterning of the gland. Depletion of endothelial cells or inhibition of VEGFR2 signaling in organ explants caused an aberrant increase in cells expressing the ductal proteins K19 and K7, with a reduction in Kit+ progenitor cells in the endbuds of reconstituted glands. Addition of exogenous endothelial cells to reconstituted glands restored epithelial patterning, as did supplementation with the endothelial cell-regulated mesenchymal factors IGFBP2 and IGFBP3. Our results demonstrate that endothelial cells promote expansion of Kit+ progenitor cells and suppress premature ductal differentiation in early developing embryonic submandibular salivary gland buds.

Triphasic differentiations of Merkel cell carcinoma in primary and metastatic lesions.

We present a rare case of Merkel cell carcinoma (MCC) with heterologous differentiation. The patient was an 86-year-old female patient with MCC who presented with a forearm skin tumor and left axillary lymph node swelling. Histopathologically, the malignant components of the primary and metastatic lesions showed the intermingled features of triphasic phenotype differentiation, which had distinct cell populations; MCC, sweat gland carcinoma (SGC) and malignant poorly differentiated spindle cells with myogenic differentiation were immunohistochemically showed. Moreover, an electron microscopic observation of the tumor cells revealed intracytoplasmic canaliculi and junctional structures that indicated ductal differentiation. To our knowledge, this is the first case of MCC admixed with SGC and sarcomatous components in both the primary and metastatic lesions. An immunohistochemical study, using several stem cell markers, indicated that the MCC arose from pluripotent epidermal stem cells.

Efficient and Controlled Generation of 2D and 3D Bile Duct Tissue from Human Pluripotent Stem Cell-Derived Spheroids.

While in vitro liver tissue engineering has been increasingly studied during the last several years, presently engineered liver tissues lack the bile duct system. The lack of bile drainage not only hinders essential digestive functions of the liver, but also leads to accumulation of bile that is toxic to hepatocytes and known to cause liver cirrhosis. Clearly, generation of bile duct tissue is essential for engineering functional and healthy liver. Differentiation of human induced pluripotent stem cells (iPSCs) to bile duct tissue requires long and/or complex culture conditions, and has been inefficient so far. Towards generating a fully functional liver containing biliary system, we have developed defined and controlled conditions for efficient 2D and 3D bile duct epithelial tissue generation. A marker for multipotent liver progenitor in both adult human liver and ductal plate in human fetal liver, EpCAM, is highly expressed in hepatic spheroids generated from human iPSCs. The EpCAM high hepatic spheroids can, not only efficiently generate a monolayer of biliary epithelial cells (cholangiocytes), in a 2D differentiation condition, but also form functional ductal structures in a 3D condition. Importantly, this EpCAM high spheroid based biliary tissue generation is significantly faster than other existing methods and does not require cell sorting. In addition, we show that a knock-in CK7 reporter human iPSC line generated by CRISPR/Cas9 genome editing technology greatly facilitates the analysis of biliary differentiation. This new ductal differentiation method will provide a more efficient method of obtaining bile duct cells and tissues, which may facilitate engineering of complete and functional liver tissue in the future.