page_title: Cytokeratin
section_title: Types
hierarchical_section_title: Cytokeratin / Types
caption_attribution_description: English: High magnification micrograph of intermediate trophoblast and an endometrial gland. Low molecular weight cytokeratin (LMWCK) immunohistochemical stain. Related images Intermed. mag. Intermed. mag. High mag. High mag. (LMWK)
context_page_description: Cytokeratins are keratin proteins found in the intracytoplasmic cytoskeleton of epithelial tissue. They are an important component of intermediate filaments, which help cells resist mechanical stress. Expression of these cytokeratins within epithelial cells is largely specific to particular organs or tissues. Thus they are used clinically to identify the cell of origin of various human tumors.
context_section_description: There are two categories of cytokeratins: the acidic type I cytokeratins and the basic or neutral type II cytokeratins. Within each category, cytokeratins are numbered in order of decreasing size, from low molecular weight (LMWCKs) to high molecular weight (HMWCKs). Cytokeratins are usually  found in heterodimeric pairs of acidic and basic subunits of similar size.
  Expression of these cytokeratins is largely organ or tissue specific. The subsets of cytokeratins which an epithelial cell expresses depends mainly on the type of epithelium, the moment in the course of terminal differentiation and the stage of development. Thus a specific cytokeratin expression profile allows the identification of epithelial cells. Furthermore, this applies also to the malignant counterparts of the epithelia, (carcinomas), as the cytokeratin profile is generally retained. Thus the study of cytokeratin expression by immunohistochemistry techniques is a tool of immense value widely used for tumor diagnosis and characterization in surgical pathology.
caption: Micrograph showing low molecular weight cytokeratin (LMWCK) staining of intermediate trophoblast (placental tissue) and endometrial glands.
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