miR-21 is mainly expressed in the tumor stroma in OSCC.

<p>(A) An overview image of miR-21 expression where the areas marked by rectangles are magnified in, (B) normal oral mucosa, (C) mild epithelial dysplasia and (D) oral squamous cell carcinoma. Mir-21 appears as a blue stain. In normal oral mucosa, (B) no miR-21 expression is observed, whereas in dysplasia, (C) a weak expression is seen in the subepithelial connective tissue, and a widespread and intense expression is found in the tumor stromal compartment (D). Panels (E), (F) and (G) illustrate combined FISH and IF for miR-21 (E), α-SMA (F) and a composite image (G) showing a high degree of overlap between the two markers.