What is a Merkel cell?
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Overview of Merkel cells
Merkel cells are found in the epidermis epidermis The outermost layer of the two main layers that make up the skin (the dermis is the deeper layer). Merkel cells normally exist in the bottom (basal) layer of the epidermis, about 0.1 mm from skin's surface. (outer layer of the skin). They were originally described in the late 1800s by Friedrich Merkel, a German anatomist. He found these cells at high density in the paws of rats and surmised they may serve as “touch cells”. Over 100 years later, although not all of the functions of Merkel cells are known, it is quite clear that they do indeed serve as touch cells and relay touch-related information such as texture and pressure to the brain. While they are present in human skin at varying levels according to body site, they are at highest density on the fingertips and lips/face where touch sensation is most acute. In addition, they produce certain hormones and are sometimes referred to as neuroendocrine neuroendocrine Neuroendocrine refers to the type of cells that make up Merkel cell carcinoma. "Neuro-" means that these cells have some sensory function related to the nervous system, while "endocrine-" refers to hormonal types of cells. Merkel cells have both such features. cells, although the reasons they produce certain hormones is unknown.
Merkel cell diagram
In the below illustration of a cross-section of skin, normal Merkel cells are shown in red and connect to nerves shown in yellow. The structures drawn include the epidermis (upper third), dermis dermis The deeper layer of the two main tissue layers that make-up the skin. The dermis is below the epidermis. Merkel cells are normally in the epidermis. In MCC, they grow and invade into the dermis and deeper structures and vessels. (middle), and deeper adipose (fatty) layer. Arteries are depicted as red and veins are blue.
Do normal Merkel cells turn into Merkel cell carcinoma?
The answer to this question is not known with certainty, but multiple lines of evidence suggest that Merkel cell carcinoma does NOT derive directly from normal Merkel cells. This is in part because it has proven impossible to get a normal Merkel cell to divide and grow. It is more likely that the precursor of a normal Merkel cell (a stem cell in the epidermis) gives rise to both the normal Merkel cell and separately, to Merkel cell carcinoma. There are several studies that have determined that normal Merkel cells are derived from epidermal precursor cells.
The following clinical publications and scientific research provide additional in-depth information about Merkel cells.